banana-pro: allow hdmi kernel messages, wait for root device

package/u-boot/files/boot.script.bpi

@@ -1,4 +1,4 @@
-setenv bootargs console=ttyS0,115200 root=/dev/mmcblk0p1
+setenv bootargs console=tty0 console=ttyS0,115200 root=/dev/mmcblk0p1 rootwait
 ext4load mmc 0:1 0x42000000 boot/${fdtfile}
 ext4load mmc 0:1 0x48000000 boot/kernel
 bootm 0x48000000 - 0x42000000