panfrost: Emulate GL_CLAMP on Bifrost

Hardware support was removed with Midgard. Use mesa/st to emulate GL_CLAMP with
nir_lower_tex automatically (the Zink lowering), and disable GL_MIRROR_CLAMP
which isn't lowered correctly.

Fixes *texwrap* Piglit tests on G52.

Fixes: f9ceab7b ("panfrost: Fix CLAMP wrap mode")
Signed-off-by: Alyssa Rosenzweig <alyssa@collabora.com>
Part-of: <!15253>
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