omap5_common: Add optargs variable for kernel command line args

Add 'optargs' variable to be set to additional kernel arguments, similar
to omap3*/am3* usage.

Cc: Sricharan R <r.sricharan@ti.com>
Signed-off-by: Tom Rini <trini@ti.com>

include/configs/omap5_common.h

@@ -150,10 +150,12 @@
 	"usbtty=cdc_acm\0" \
 	"vram=16M\0" \
 	"partitions=" PARTS_DEFAULT "\0" \
+	"optargs=\0" \
 	"mmcdev=0\0" \
 	"mmcroot=/dev/mmcblk0p2 rw\0" \
 	"mmcrootfstype=ext4 rootwait\0" \
 	"mmcargs=setenv bootargs console=${console} " \
+		"${optargs} " \
 		"vram=${vram} " \
 		"root=${mmcroot} " \
 		"rootfstype=${mmcrootfstype}\0" \