ARM: dts: OMAP: Rename pandaES and var_som for consistency

Rename the files to have names consistent across OMAP boards.

Update the Makefile to use the new name.
Signed-off-by: NBenoit Cousson <b-cousson@ti.com>

arch/arm/boot/dts/Makefile

@@ -68,8 +68,8 @@ dtb-$(CONFIG_ARCH_OMAP2PLUS) += omap2420-h4.dtb \
 	omap3-evm.dtb \
 	omap3-tobi.dtb \
 	omap4-panda.dtb \
-	omap4-pandaES.dtb \
-	omap4-var_som.dtb \
+	omap4-panda-es.dtb \
+	omap4-var-som.dtb \
 	omap4-sdp.dtb \
 	omap5-evm.dtb \
 	am335x-evm.dtb \