drm/vmwgfx: Mark a surface gpu-dirty after the SVGA3dCmdDXGenMips command

The SVGA3dCmdDXGenMips command uses a shader-resource view to access
the underlying surface. Normally accesses using that view-type are not
dirtying the underlying surface, but that particular command is an
exception.
Mark the surface gpu-dirty after a SVGA3dCmdDXGenMips command has been
submitted.

This fixes the piglit getteximage-formats test run with
SVGA_FORCE_COHERENT=1

Fixes: a9f58c45

 ("drm/vmwgfx: Be more restrictive when dirtying resources")
Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Charmaine Lee <charmainel@vmware.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>
Signed-off-by: Zack Rusin <zackr@vmware.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210505035740.286923-3-zackr@vmware.com