staging/xgifb: Use SiS structs

This patch replaces some of the XGI internal structs by their
counterparts in the SiS driver.
XGI330_LVDSDataStruct -> SiS_LVDSData
XGI330_LCDDataStruct -> SiS_LCDData
XGI330_CHTVDataStruct -> SiS_LVDSData

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