ARM: dts: Add build target for omap4-panda-a4

Commit 0d9250c (ARM: dts: omap4-panda: Add pinmux configuration for
HDMI) added a new device-tree source file for Rev A4 of the OMAP4430
Panda board but it did not add this version to the makefile. Hence,
add this file to the makefile.

Signed-off-by: Jon Hunter <jon-hunter@ti.com>
Signed-off-by: Tony Lindgren <tony@atomide.com>

arch/arm/boot/dts/Makefile

@@ -105,6 +105,7 @@ dtb-$(CONFIG_ARCH_OMAP2PLUS) += omap2420-h4.dtb \
 	omap3-evm.dtb \
 	omap3-tobi.dtb \
 	omap4-panda.dtb \
+	omap4-panda-a4.dtb \
 	omap4-panda-es.dtb \
 	omap4-var-som.dtb \
 	omap4-sdp.dtb \