staging/xgifb: Consolidate if/else for 'identical' branches

Since XGI_LCDDesStruct is fully contained in XGI330_LCDDataDesStruct2
and the offsets for the first members is identical we can consolidate
the if/else branches here and use XGI330_LCDDataDesStruct2 for
everything.

Signed-off-by: Peter Huewe <peterhuewe@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>