meta: Refactor code for binding a texture image to the FBO.

meta: Refactor code for binding a texture image to the FBO.

Almost the exact same code appeared twice, and it needs to expand to
handle additional texture targets.  Refactor it to tidy up the code and
avoid duplicating more work in the future.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Matt Turner <mattst88@gmail.com>
Reviewed-by: Anuj Phogat <anuj.phogat@gmail.com>
Reviewed-by: Ian Romanick <ian.d.romanick@intel.com>