v3d: Use driconf to expose non-MSAA texture limits for Xorg.

v3d: Use driconf to expose non-MSAA texture limits for Xorg.

The V3D 4.2 HW has a limit to MSAA texture sizes of 4096.  With non-MSAA,
we can go up to 7680 (actually probably 8138, but that hasn't been
validated by the HW team).  Exposing 7680 in X11 will allow dual 4k displays.