common: convert makefiles to Kbuild style

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/common/spl/Makefile b/common/spl/Makefile
index e8144f7..5c0637b 100644
--- a/common/spl/Makefile
+++ b/common/spl/Makefile
@@ -8,34 +8,12 @@
 # Based on common/Makefile.
 #
 
-include $(TOPDIR)/config.mk
-
-LIB	= $(obj)libspl.o
-
 ifdef CONFIG_SPL_BUILD
-COBJS-$(CONFIG_SPL_FRAMEWORK) += spl.o
-COBJS-$(CONFIG_SPL_NOR_SUPPORT) += spl_nor.o
-COBJS-$(CONFIG_SPL_YMODEM_SUPPORT) += spl_ymodem.o
-COBJS-$(CONFIG_SPL_NAND_SUPPORT) += spl_nand.o
-COBJS-$(CONFIG_SPL_ONENAND_SUPPORT) += spl_onenand.o
-COBJS-$(CONFIG_SPL_NET_SUPPORT) += spl_net.o
-COBJS-$(CONFIG_SPL_MMC_SUPPORT) += spl_mmc.o
+obj-$(CONFIG_SPL_FRAMEWORK) += spl.o
+obj-$(CONFIG_SPL_NOR_SUPPORT) += spl_nor.o
+obj-$(CONFIG_SPL_YMODEM_SUPPORT) += spl_ymodem.o
+obj-$(CONFIG_SPL_NAND_SUPPORT) += spl_nand.o
+obj-$(CONFIG_SPL_ONENAND_SUPPORT) += spl_onenand.o
+obj-$(CONFIG_SPL_NET_SUPPORT) += spl_net.o
+obj-$(CONFIG_SPL_MMC_SUPPORT) += spl_mmc.o
 endif
-
-COBJS	:= $(sort $(COBJS-y))
-SRCS	:= $(COBJS:.o=.c)
-OBJS	:= $(addprefix $(obj),$(COBJS-y))
-
-all:	$(obj).depend $(LIB)
-
-$(LIB):	$(OBJS)
-	$(call cmd_link_o_target, $(OBJS))
-
-#########################################################################
-
-# defines $(obj).depend target
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
-
-#########################################################################