Adds support for MGA DRM version 3.2.

Adds support for MGA DRM version 3.2.

This patch makes use of two of the new ioctls added in MGA DRM version
3.2.  Specifically, the DRM_MGA_SET_FENCE and DRM_MGA_WAIT_FENCE
ioctls are used in mgaWaitForFrameCompletion.  As a result the MMIO
register region and the primary DMA region are *not* mapped (if DRM
3.2 is available).

This patch does *not* make use of the new get_param query was added to
differentiate between G4x0 cards and G550 cards.  That is left to a
future update.

Xorg bug: 3259
Reviewed by: Eric Anholt