grub-efi: Add support for emuarm-efi

oe-core avoids armv7ve builds. This is more of a blanket fix because
grub supports this arch. It doesn't support hardfp configuration that
can't be forced into softfp with a compiler flag. qemuarm-efi defaults
to softfp.

Signed-off-by: Andrei Gherzan <andrei.gherzan@huawei.com>