Add uefi bios loading support, now only uefi bios is porting to
loongarch virt machine.

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Xiaojuan Yang <yangxiaojuan@loongson.cn>
Message-Id: <20220712083206.4187715-3-yangxiaojuan@loongson.cn>
Signed-off-by: Richard Henderson <richard.henderson@linaro.org>