r300: enable nir_move_vec_src_uses_to_dest

r300: enable nir_move_vec_src_uses_to_dest

We want to do this in general, right now the stats are not that good but
that will be taken care of in the next commits.

RV530:
total instructions in shared programs: 93561 -> 93597 (0.04%)
instructions in affected programs: 39015 -> 39051 (0.09%)
helped: 207
HURT: 212
total temps in shared programs: 12864 -> 13019 (1.20%)
temps in affected programs: 2010 -> 2165 (7.71%)
helped: 57
HURT: 181
total cycles in shared programs: 144639 -> 144506 (-0.09%)
cycles in affected programs: 54524 -> 54391 (-0.24%)
helped: 191
HURT: 234

RV370:
total instructions in shared programs: 63692 -> 63811 (0.19%)
instructions in affected programs: 16851 -> 16970 (0.71%)
helped: 121
HURT: 141
total temps in shared programs: 9966 -> 10050 (0.84%)
temps in affected programs: 969 -> 1053 (8.67%)
helped: 33
HURT: 126
total cycles in shared programs: 101042 -> 101205 (0.16%)
cycles in affected programs: 20606 -> 20769 (0.79%)
helped: 121
HURT: 155

Reviewed-by: Emma Anholt <emma@anholt.net>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24932>