pan/mdg: Fix 16-bit alignment with spiller
The loop over sources has to happen for every instruction, regardless of whether we also need to register allocate the destination. The other source loops handle this properly, but this one was missed.
Fixes spilling failure in shaders/android/angle/aztec_ruins/16.shader_test when the input NIR is shuffled a bit (from reordering passes).
Fixes: 129d390b ("pan/mdg: Fix bound setting in RA for sources") Signed-off-by: Alyssa Rosenzweig alyssa@collabora.com