[Mesa-dev] drisw: fix regression with shm put image paths

[Dave Airlie]

Back with
    drisw: use putImageShm if available

this caused a regression when moving a window with mutter
off the edge of the screen in swrast mode.

I traced this down to the X server shm sizing checks, where
it validates the image offset can fit the height * stride
passed. Unfortunately since we added the src x offset to
the shm offset, this failed.

This series allows the driver to control the src x, y
and fixes the drisw paths to passes the src x offset instead
of adding it to the image offset calculations.

Dave.