r300: respect output_semantic_index when writing colors

r300: respect output_semantic_index when writing colors

Right now we don't explicitly check it and we expect that the
output_semantic_index array is always ordered. Unfortunately,
this is not the case since 74c02d99b224fbc02132b54bf23e6ac1e117d805

Fixes corruption in Amnesia: the Dark Descent.

cc: mesa-stable

Closes: https://gitlab.freedesktop.org/mesa/mesa/-/issues/6179
Signed-off-by: Pavel Ondračka <pavel.ondracka@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/15523>