Staging: xgifb: fix braces {} are not necessary for any arm of this statement

Fix checkpatch.pl issues with braces {} are not necessary
for any arm of this statement in vb_setmode.c

Signed-off-by: Ebru Akagunduz <ebru.akagunduz@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>