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/davinci/Makefile b/arch/arm/cpu/arm926ejs/davinci/Makefile
index b596818..7d67191 100644
--- a/arch/arm/cpu/arm926ejs/davinci/Makefile
+++ b/arch/arm/cpu/arm926ejs/davinci/Makefile
@@ -7,44 +7,22 @@
 # SPDX-License-Identifier:	GPL-2.0+
 #
 
-include $(TOPDIR)/config.mk
-
-LIB	= $(obj)lib$(SOC).o
-
-COBJS-y				+= cpu.o misc.o timer.o psc.o pinmux.o reset.o
-COBJS-$(CONFIG_DA850_LOWLEVEL)	+= da850_lowlevel.o
-COBJS-$(CONFIG_SOC_DM355)	+= dm355.o
-COBJS-$(CONFIG_SOC_DM365)	+= dm365.o
-COBJS-$(CONFIG_SOC_DM644X)	+= dm644x.o
-COBJS-$(CONFIG_SOC_DM646X)	+= dm646x.o
-COBJS-$(CONFIG_SOC_DA830)	+= da830_pinmux.o
-COBJS-$(CONFIG_SOC_DA850)	+= da850_pinmux.o
-COBJS-$(CONFIG_DRIVER_TI_EMAC)	+= lxt972.o dp83848.o et1011c.o ksz8873.o
+obj-y				+= cpu.o misc.o timer.o psc.o pinmux.o reset.o
+obj-$(CONFIG_DA850_LOWLEVEL)	+= da850_lowlevel.o
+obj-$(CONFIG_SOC_DM355)	+= dm355.o
+obj-$(CONFIG_SOC_DM365)	+= dm365.o
+obj-$(CONFIG_SOC_DM644X)	+= dm644x.o
+obj-$(CONFIG_SOC_DM646X)	+= dm646x.o
+obj-$(CONFIG_SOC_DA830)	+= da830_pinmux.o
+obj-$(CONFIG_SOC_DA850)	+= da850_pinmux.o
+obj-$(CONFIG_DRIVER_TI_EMAC)	+= lxt972.o dp83848.o et1011c.o ksz8873.o
 
 ifdef CONFIG_SPL_BUILD
-COBJS-$(CONFIG_SPL_FRAMEWORK)	+= spl.o
-COBJS-$(CONFIG_SOC_DM365)	+= dm365_lowlevel.o
-COBJS-$(CONFIG_SOC_DA8XX)	+= da850_lowlevel.o
+obj-$(CONFIG_SPL_FRAMEWORK)	+= spl.o
+obj-$(CONFIG_SOC_DM365)	+= dm365_lowlevel.o
+obj-$(CONFIG_SOC_DA8XX)	+= da850_lowlevel.o
 endif
 
 ifndef CONFIG_SKIP_LOWLEVEL_INIT
-SOBJS	+= lowlevel_init.o
+obj-y	+= lowlevel_init.o
 endif
-
-SRCS	:= $(START:.o=.S) $(SOBJS:.o=.S) $(COBJS-y:.o=.c)
-OBJS	:= $(addprefix $(obj),$(COBJS-y) $(SOBJS))
-START	:= $(addprefix $(obj),$(START))
-
-all:	$(obj).depend $(LIB)
-
-$(LIB):	$(OBJS)
-	$(call cmd_link_o_target, $(OBJS))
-
-#########################################################################
-
-# defines $(obj).depend target
-include $(SRCTREE)/rules.mk
-
-sinclude $(obj).depend
-
-#########################################################################