c6x: enable building all dtbs

Enable the 'dtbs' target for c6x. This allows building all the dts
files in arch/c6x/boot/dts/ for enabled platforms or when
COMPILE_TEST and OF_ALL_DTBS are enabled.

Cc: Mark Salter <msalter@redhat.com>
Cc: Aurelien Jacquiot <jacquiot.aurelien@gmail.com>
Cc: linux-c6x-dev@linux-c6x.org
Signed-off-by: Rob Herring <robh@kernel.org>

arch/c6x/boot/dts/Makefile

@@ -5,6 +5,12 @@
 
 DTC_FLAGS ?= -p 1024
 
+dtb-$(CONFIG_SOC_TMS320C6455) += dsk6455.dtb
+dtb-$(CONFIG_SOC_TMS320C6457) += evmc6457.dtb
+dtb-$(CONFIG_SOC_TMS320C6472) += evmc6472.dtb
+dtb-$(CONFIG_SOC_TMS320C6474) += evmc6474.dtb
+dtb-$(CONFIG_SOC_TMS320C6678) += evmc6678.dtb
+
 ifneq ($(DTB),)
 obj-y += $(DTB).dtb.o
 endif