r600g: Use blitter rather than DMA for 128bpp on cayman (v3)

r600g: Use blitter rather than DMA for 128bpp on cayman (v3)

On cayman, 128bpp surfaces require non_disp ordering for hw
access to both linear and tiled surfaces.  When we use the 3D
engine we can set the non_disp ordering on both the tiled and
linear sides (via CB or texture), but when we use the DMA
engine, we can only set the non_disp ordering on the tiled
side, so after a L2T operation with the DMA engine, the data
ends up in the wrong order on the tiled side.

v2: cayman/TN only

v3: fix comments

Fixes:
https://bugs.freedesktop.org/show_bug.cgi?id=60802

Note: this is a candidate for the 9.1 branch.

Signed-off-by: Alex Deucher <alexander.deucher@amd.com>