uboot-phytec

arm64: ls1046ardb: Add distro boot support

Tested on ls1046ardb with automatically boot Ubuntu from SD card or
USB disk, if it fails to detect external storage disk, fall back to
qspi boot.

Signed-off-by: Shengzhou Liu <Shengzhou.Liu@nxp.com>
Signed-off-by: Gong Qianyu <Qianyu.Gong@nxp.com>
Reviewed-by: York Sun <york.sun@nxp.com>