uefi.sh: allow uefi boot script be used on rdn2 platform

Allow RD-N2 platform to use the UEFI boot script to validate boot upto
a edk2 efi shell.

Signed-off-by: Thomas Abraham <thomas.abraham@arm.com>
Change-Id: I36a021300762de3e4e9e43bb937f7458bd1a3860