ARM: dts: Build all keystone dt blobs

Now we have additional two SOC/boards supported, so add
make file rule so that all device tree blobs can be build
for keystone with 'make dtbs'.
Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti.com>

arch/arm/boot/dts/Makefile

@@ -81,6 +81,9 @@ dtb-$(CONFIG_ARCH_HIGHBANK) += highbank.dtb \
 	ecx-2000.dtb
 dtb-$(CONFIG_ARCH_INTEGRATOR) += integratorap.dtb \
 	integratorcp.dtb
+dtb-$(CONFIG_ARCH_KEYSTONE) += k2hk-evm.dtb \
+	k2l-evm.dtb \
+	k2e-evm.dtb
 dtb-$(CONFIG_ARCH_LPC32XX) += ea3250.dtb phy3250.dtb
 dtb-$(CONFIG_ARCH_KIRKWOOD) += kirkwood-cloudbox.dtb \
 	kirkwood-db-88f6281.dtb \