uboot-imx

ARM: uniphier: carry on booting for Unknown boot mode

No need to stop booting U-Boot even if boot mode is unknown.
Setting the "bootmode" environment is only useful for booting
Linux Kernel.  Anyway, U-Boot has already booted by this point.

Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>