odroid-go2: do not disable EFI

Remove the unset of the EFI loader, it's possible for U-Boot to
provide a EFI environment on this board, and it's also required by
the FreeBSD loader which mandated EFI on Aarch64.

Signed-off-by: Roger Pau Monné <royger@FreeBSD.org>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>