x86: qemu: Mark ucode as optional for SPL in u-boot.dtsi

QEMU does not need ucode and this is indicated in u-boot.dtsi
for U-Boot proper. Now add the same for SPL.

Signed-off-by: Bin Meng <bmeng.cn@gmail.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed