arm926ejs: convert makefiles to Kbuild style

Note1:
In arch/arm/cpu/arm926ejs/spear/Makefile
START := start.o
was changed
extra-$(CONFIG_SPL_BUILD) := start.o
because spear/start.o is only used for SPL.

Note2:
START := start.o
was missing from arch/arm/cpu/arm926ejs/mxs/Makefile.
This commit simply adds
extra-$(CONFIG_SPL_BUILD) := start.o

Signed-off-by: Masahiro Yamada <yamada.m@jp.panasonic.com>
diff --git a/arch/arm/cpu/arm926ejs/mxs/Makefile b/arch/arm/cpu/arm926ejs/mxs/Makefile
index 3d66892..13b5a54 100644
--- a/arch/arm/cpu/arm926ejs/mxs/Makefile
+++ b/arch/arm/cpu/arm926ejs/mxs/Makefile
@@ -5,25 +5,14 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-include $(TOPDIR)/config.mk
+extra-$(CONFIG_SPL_BUILD) := start.o
 
-LIB	= $(obj)lib$(SOC).o
-
-COBJS	= clock.o mxs.o iomux.o timer.o
+obj-y	= clock.o mxs.o iomux.o timer.o
 
 ifdef	CONFIG_SPL_BUILD
-COBJS	+= spl_boot.o spl_lradc_init.o spl_mem_init.o spl_power_init.o
+obj-y	+= spl_boot.o spl_lradc_init.o spl_mem_init.o spl_power_init.o
 endif
 
-SRCS	:= $(START:.o=.S) $(COBJS:.o=.c)
-OBJS	:= $(addprefix $(obj),$(COBJS))
-START	:= $(addprefix $(obj),$(START))
-
-all:	$(obj).depend $(LIB)
-
-$(LIB):	$(OBJS)
-	$(call cmd_link_o_target, $(OBJS))
-
 # Specify the target for use in elftosb call
 ELFTOSB_TARGET-$(CONFIG_MX23) = imx23
 ELFTOSB_TARGET-$(CONFIG_MX28) = imx28
@@ -33,12 +22,3 @@
 
 $(OBJTREE)/u-boot.sb: $(OBJTREE)/u-boot.bin $(OBJTREE)/spl/u-boot-spl.bin $(OBJTREE)/u-boot.bd
 		elftosb -zf $(ELFTOSB_TARGET-y) -c $(OBJTREE)/u-boot.bd -o $(OBJTREE)/u-boot.sb
-
-#########################################################################
-
-# defines $(obj).depend target
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
-
-#########################################################################