stand: Fix build failure due to old EDK2 interface

In 43b8edb320519, we change EFI_GRAPHICS_OUTPUT_PROTOCOL from
EFI_GRAPHICS_OUTPUT. However, this patch is not MFC to stable/15. As a
result, we need to use the old interface to prevent compile failure.

Fixes: 1802f2ca7215
Sponsored by: The FreeBSD Foundation