panfrost: use RGB1 component ordering for R5G6B5 pixel formats
For some purposes (e.g. advanced blending) we need a non-zero alpha value returned from reads. This is only guaranteed on Bifrost if we explicitly request RGB1 component ordering. The default is to use RGBA component ordering, which for R5G6B5 causes 0 to be read for alpha. A complication is that the Mali fixed function hardware requires four components (which implies RGBA rather than RGB1). If fixed function blending is in use, we modify the pixel format back to RGBA when building the blend descriptor. Cc: mesa-stable Reviewed-by:Boris Brezillon <boris.brezillon@collabora.com> Reviewed-by:
Mary Guillemard <mary.guillemard@collabora.com> Part-of: <mesa/mesa!29606> (cherry picked from commit 004e0eb3)