efi/x86: Mark setup_graphics static

This function is only called from efi_main in the same source file.

Signed-off-by: Arvind Sankar <nivedita@alum.mit.edu>
Link: https://lore.kernel.org/r/20200130222004.1932152-1-nivedita@alum.mit.edu


Signed-off-by: Ard Biesheuvel <ardb@kernel.org>