mesa: Refactor update_array_format to make _mesa_update_array_format_public

mesa: Refactor update_array_format to make _mesa_update_array_format_public

Pulls the parts of update_array_format that aren't just parameter
validation out into a function that can be called from other parts of
Mesa (e.g., meta).

Signed-off-by: Ian Romanick <ian.d.romanick@intel.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
(cherry picked from commit a336fcd36a4743c1ea6f8549cb31b48277359717)