x86: qemu: Add required linux/sizes.h include

These files rely on the config.h file provided this include. Add it
explictily so we can move to a text environment.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> # Intel Edison
Reviewed-by: Bin Meng <bmeng.cn@gmail.com>