ARM: build dtbs depending on CONFIG_OFTREE

The upcoming multi image support will need devicetree binary
blobs even when there is no builtin dtb. Instead of depending
on CONFIG_BUILTIN_DTB depend on CONFIG_OFTREE and let this option
select DTC.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

arch/arm/Makefile

@@ -328,7 +328,7 @@ endif
 common-y += $(BOARD) $(MACH)
 common-y += arch/arm/lib/ arch/arm/cpu/
 
-common-$(CONFIG_BUILTIN_DTB) += arch/arm/dts/
+common-$(CONFIG_OFTREE) += arch/arm/dts/
 
 lds-y	:= arch/arm/lib/barebox.lds
 

drivers/of/Kconfig

@@ -1,4 +1,5 @@
 config OFTREE
+	select DTC
 	bool
 
 config OFTREE_MEM_GENERIC