uboot-omap: add 'rootwait' to the kernel cmdline

Some SD cards take a while to get detected, fix booting of those.

Signed-off-by: Andre Heider <a.heider@gmail.com>

package/boot/uboot-omap/files/uEnv-default.txt

@@ -5,4 +5,4 @@ fdtdir=/dtbs
 uenvcmd=run loadfdt; run loadimage; run uenvbootargs ; bootz ${loadaddr} - ${fdtaddr}
 loadfdt=load mmc ${bootpart} ${fdtaddr} ${fdtdir}/${fdtfile}
 devtype=mmc
-uenvbootargs=setenv bootargs console=${console} root=/dev/mmcblk0p2
+uenvbootargs=setenv bootargs console=${console} root=/dev/mmcblk0p2 rootwait