drivers: convert makefiles to Kbuild style

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/drivers/sound/Makefile b/drivers/sound/Makefile
index c50dd15..6d25292 100644
--- a/drivers/sound/Makefile
+++ b/drivers/sound/Makefile
@@ -5,29 +5,7 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-include $(TOPDIR)/config.mk
-
-LIB	:= $(obj)libsound.o
-
-COBJS-$(CONFIG_SOUND)	+= sound.o
-COBJS-$(CONFIG_I2S)	+= samsung-i2s.o
-COBJS-$(CONFIG_SOUND_WM8994)	+= wm8994.o
-COBJS-$(CONFIG_SOUND_MAX98095)	+= max98095.o
-
-COBJS	:= $(COBJS-y)
-SRCS	:= $(COBJS:.o=.c)
-OBJS	:= $(addprefix $(obj),$(COBJS))
-
-all:	$(LIB)
-
-$(LIB):	$(obj).depend $(OBJS)
-	$(call cmd_link_o_target, $(OBJS))
-
-#########################################################################
-
-# defines $(obj).depend target
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
-
-#
+obj-$(CONFIG_SOUND)	+= sound.o
+obj-$(CONFIG_I2S)	+= samsung-i2s.o
+obj-$(CONFIG_SOUND_WM8994)	+= wm8994.o
+obj-$(CONFIG_SOUND_MAX98095)	+= max98095.o