ppc/85xx: Split out cpu_init_early into its own file for NAND_SPL

By pulling out cpu_init_early we can build just it and not all of
cpu_init for NAND_SPL.

Signed-off-by: Kumar Gala <galak@kernel.crashing.org>
diff --git a/cpu/mpc85xx/Makefile b/cpu/mpc85xx/Makefile
index a177f42..3ef00e8 100644
--- a/cpu/mpc85xx/Makefile
+++ b/cpu/mpc85xx/Makefile
@@ -65,6 +65,7 @@
 COBJS	= $(COBJS-y)
 COBJS	+= cpu.o
 COBJS	+= cpu_init.o
+COBJS	+= cpu_init_early.o
 COBJS	+= interrupts.o
 COBJS	+= speed.o
 COBJS	+= tlb.o