x86: Run QEMU machine setup in SPL

Call the hardware-init function from QEMU from SPL. This allows the
video BIOS to operate correctly.

Create an x86-wide qemu.h header to avoid having to #ifdef the header
in spl.c

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>
Tested-by: Bin Meng <bmeng.cn@gmail.com> # qemu-x86_64