sna: Use inplace X tiling for LLC uploads

Based on a suggestion by Chad Versace (taken from a patch for mesa).

This allows for a faster upload of pixel data through a ShmImage, or for
complete replacement of a GPU bo.

Using a modified version of x11perf to upload to a pixmap rather than
scanout on an IVB i7-3720qm:

Before:
40000000 trep @   0.0007 msec (1410000.0/sec): ShmPutImage 10x10 square
 4000000 trep @   0.0110 msec (  90700.0/sec): ShmPutImage 100x100 square
  160000 trep @   0.1689 msec (   5920.0/sec): ShmPutImage 500x500 square

After:
40000000 trep @   0.0007 msec (1450000.0/sec): ShmPutImage 10x10 square
 6000000 trep @   0.0061 msec ( 164000.0/sec): ShmPutImage 100x100 square
  400000 trep @   0.1126 msec (   8880.0/sec): ShmPutImage 500x500 square

However, the real takeaway from this is that the overheads for
ShmPutImage are substantial, only hitting around 70% expected efficiency,
and overshadowed by PutImage, which for reference is

60000000 trep @   0.0006 msec (1800000.0/sec): PutImage 10x10 square

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

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