gallium: Mute arrays for several meta like callbacks.

gallium: Mute arrays for several meta like callbacks.

Set the _DrawArray pointer to NULL when calling into the Drivers
Bitmap/CopyPixels/DrawAtlasBitmaps/DrawPixels/DrawTex hooks.
This fixes an assert that gets uncovered when the following
patch gets applied.

v2: Mute from within the state tracker instead of generic mesa.
v3: Avoid evaluating _DrawArrays from within st_validate_state.

Signed-off-by: Mathias Fröhlich <Mathias.Froehlich@web.de>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>