staging: xgifb: vb_setmode: delete IF_DEF_YPbPr checks

Code checking for IF_DEF_YPbPr is only executed for chips < XG20, and
there IF_DEF_YPbPr is always true, so the flag is redundant.

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>