staging/xgifb: Remove unneeded conditional assignment

pVBInfo->ram_type is assigned the return value of
XGINew_GetXG20DRAMType which can only be 0, 1 or 2

-> The conditional assignment is not needed here as it always evaluates
to true.
-> remove

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