xf86-video-mga: Fix to always set HiPri for G200e4 V2

  - Changed the HiPri value for G200e4 to always be 0.
  - Added Bandwith limitation to block resolution above 1920x1200x60Hz

  - (V2): Pulled out ulMemoryBandwidth of condition so it's always initialized
        as reviewed by : Stefan Dirsch <sndirsch@suse.de>

Reviewed-by: Samer El-Haj-Mahmoud <smahmoud@lenovo.com>