powerpc: convert makefiles to Kbuild style

Note:
arch/powerpc/cpu/mpc8260/Makefile is originally like follows:

    ---<snip>---
    START   = start.o kgdb.o
    COBJS   = traps.o serial_smc.o serial_scc.o cpu.o cpu_init.o speed.o \
    ---<snip>---
    COBJS-$(CONFIG_ETHER_ON_SCC) = ether_scc.o
    ---<snip>---
    $(LIB): $(OBJS)
            $(call cmd_link_o_target, $(OBJS) $(obj)kgdb.o)

The link rule `$(call cmd_link_o_target, $(OBJS) $(obj)kgdb.o)'
is weird.
kbdg.o is not included in $(OBJS) but linked into $(LIB)
and $(LIB) is not dependent on kgdb.o.
(Broken dependency tracking)

So,
    START   = start.o kgdb.o
shoud have been
    START   = start.o
    SOBJS   = kgdb.o

That is why this commit adds kgdb.o to obj-y, not to extra-y.

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Wolfgang Denk <wd@denx.de>
Cc: Stefan Roese <sr@denx.de>
diff --git a/arch/powerpc/cpu/mpc8xxx/Makefile b/arch/powerpc/cpu/mpc8xxx/Makefile
index 3dc8e05..395fed1 100644
--- a/arch/powerpc/cpu/mpc8xxx/Makefile
+++ b/arch/powerpc/cpu/mpc8xxx/Makefile
@@ -6,10 +6,6 @@
 # Version 2 as published by the Free Software Foundation.
 #
 
-include $(TOPDIR)/config.mk
-
-LIB	= $(obj)lib8xxx.o
-
 MINIMAL=
 
 ifdef CONFIG_SPL_BUILD
@@ -20,30 +16,18 @@
 
 ifdef MINIMAL
 
-COBJS-$(CONFIG_FSL_LAW) += law.o
+obj-$(CONFIG_FSL_LAW) += law.o
 
 else
 
 ifneq ($(CPU),mpc83xx)
-COBJS-y	+= cpu.o
+obj-y	+= cpu.o
 endif
 
-COBJS-$(CONFIG_OF_LIBFDT) += fdt.o
-COBJS-$(CONFIG_FSL_IFC) += fsl_ifc.o
-COBJS-$(CONFIG_FSL_LBC) += fsl_lbc.o
-COBJS-$(CONFIG_SYS_SRIO) += srio.o
-COBJS-$(CONFIG_FSL_LAW) += law.o
+obj-$(CONFIG_OF_LIBFDT) += fdt.o
+obj-$(CONFIG_FSL_IFC) += fsl_ifc.o
+obj-$(CONFIG_FSL_LBC) += fsl_lbc.o
+obj-$(CONFIG_SYS_SRIO) += srio.o
+obj-$(CONFIG_FSL_LAW) += law.o
 
 endif
-
-SRCS	:= $(START:.o=.S) $(SOBJS-y:.o=.S) $(COBJS-y:.o=.c)
-OBJS	:= $(addprefix $(obj),$(SOBJS-y) $(COBJS-y))
-
-all:	$(obj).depend $(LIB)
-
-$(LIB):	$(OBJS)
-	$(call cmd_link_o_target, $(OBJS))
-
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
diff --git a/arch/powerpc/cpu/mpc8xxx/ddr/Makefile b/arch/powerpc/cpu/mpc8xxx/ddr/Makefile
index 29523aa..8cbc06c 100644
--- a/arch/powerpc/cpu/mpc8xxx/ddr/Makefile
+++ b/arch/powerpc/cpu/mpc8xxx/ddr/Makefile
@@ -6,17 +6,13 @@
 # Version 2 as published by the Free Software Foundation.
 #
 
-include $(TOPDIR)/config.mk
-
-LIB	= $(obj)libddr.o
-
-COBJS-$(CONFIG_FSL_DDR1)	+= main.o util.o ctrl_regs.o options.o \
+obj-$(CONFIG_FSL_DDR1)	+= main.o util.o ctrl_regs.o options.o \
 				   lc_common_dimm_params.o
 
-COBJS-$(CONFIG_FSL_DDR2)	+= main.o util.o ctrl_regs.o options.o \
+obj-$(CONFIG_FSL_DDR2)	+= main.o util.o ctrl_regs.o options.o \
 				   lc_common_dimm_params.o
 
-COBJS-$(CONFIG_FSL_DDR3)	+= main.o util.o ctrl_regs.o options.o \
+obj-$(CONFIG_FSL_DDR3)	+= main.o util.o ctrl_regs.o options.o \
 				   lc_common_dimm_params.o
 ifdef CONFIG_DDR_SPD
 SPD := y
@@ -25,21 +21,9 @@
 SPD := y
 endif
 ifdef SPD
-COBJS-$(CONFIG_FSL_DDR1)	+= ddr1_dimm_params.o
-COBJS-$(CONFIG_FSL_DDR2)	+= ddr2_dimm_params.o
-COBJS-$(CONFIG_FSL_DDR3)	+= ddr3_dimm_params.o
+obj-$(CONFIG_FSL_DDR1)	+= ddr1_dimm_params.o
+obj-$(CONFIG_FSL_DDR2)	+= ddr2_dimm_params.o
+obj-$(CONFIG_FSL_DDR3)	+= ddr3_dimm_params.o
 endif
 
-COBJS-$(CONFIG_FSL_DDR_INTERACTIVE) += interactive.o
-
-SRCS	:= $(START:.o=.S) $(SOBJS-y:.o=.S) $(COBJS-y:.o=.c)
-OBJS	:= $(addprefix $(obj),$(SOBJS-y) $(COBJS-y))
-
-all:	$(obj).depend $(LIB)
-
-$(LIB):	$(OBJS)
-	$(call cmd_link_o_target, $(OBJS))
-
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
+obj-$(CONFIG_FSL_DDR_INTERACTIVE) += interactive.o