ARM: convert build of appended dtb zImage to list of dtbs

Allow CONFIG_BUILD_ARM_APPENDED_DTB_IMAGE_NAMES to specify
a space separated list of dtbs to append to the zImage,
and name the resulting file zImage-dtb

Change-Id: Ied5d0bafbd1d01fc1f109c15c4283de7029903c9
Signed-off-by: Colin Cross <ccross@android.com>
diff --git a/arch/arm/Makefile b/arch/arm/Makefile
index 0ff187a..b53a7b4 100644
--- a/arch/arm/Makefile
+++ b/arch/arm/Makefile
@@ -299,7 +299,7 @@
 ifeq ($(CONFIG_XIP_KERNEL),y)
 KBUILD_IMAGE := xipImage
 else ifeq ($(CONFIG_BUILD_ARM_APPENDED_DTB_IMAGE),y)
-KBUILD_IMAGE := zImage-dtb.$(CONFIG_BUILD_ARM_APPENDED_DTB_IMAGE_NAME)
+KBUILD_IMAGE := zImage-dtb
 else
 KBUILD_IMAGE := zImage
 endif
@@ -351,6 +351,9 @@
 	$(Q)$(MAKE) $(build)=arch/arm/vdso $@
 endif
 
+zImage-dtb: vmlinux scripts dtbs
+	$(Q)$(MAKE) $(build)=$(boot) MACHINE=$(MACHINE) $(boot)/$@
+
 # We use MRPROPER_FILES and CLEAN_FILES now
 archclean:
 	$(Q)$(MAKE) $(clean)=$(boot)