panfrost: Fix gl_FragColor lowering
The gl_FragColor lowering in the fragment shader depends on the number of render targets, which can change every set_framebuffer_state. set_framebuffer_state thus needs to force a rebind of the fragment shader.
Fixes a regression in Piglit fbo-drawbuffers-none gl_FragColor -auto -fbo from enabling AFBC on Mali G52.
Fixes: 28ac4d1e ("panfrost: Call nir_lower_fragcolor based on key") Signed-off-by: Alyssa Rosenzweig alyssa@collabora.com