mesa: refactor get_texture_image to remove duplicate code

Move shared code in a new function (_get_texture_image) and use it instead
of duplicating the same lines.
Will be also used by the EXT_dsa functions (GetTextureImageEXT and GetMultiTexImageEXT).

Reviewed-by: Marek Olšák <marek.olsak@amd.com>
1 file changed