aco: apply literals to split mads

aco: apply literals to split mads

Removing the return is also needed to apply literals to mads (which can be
done on GFX10).

pipeline-db (Navi):
Totals from affected shaders:
SGPRS: 368787 -> 367555 (-0.33 %)
VGPRS: 312436 -> 312448 (0.00 %)
Spilled SGPRs: 461 -> 461 (0.00 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Code Size: 26113388 -> 26098260 (-0.06 %) bytes
Max Waves: 35982 -> 35982 (0.00 %)
Instructions: 5038670 -> 5028941 (-0.19 %)

pipeline-db (Vega):
Totals from affected shaders:
SGPRS: 369843 -> 368659 (-0.32 %)
VGPRS: 317224 -> 317196 (-0.01 %)
Spilled SGPRs: 629 -> 629 (0.00 %)
Spilled VGPRs: 0 -> 0 (0.00 %)
Code Size: 26310540 -> 26295156 (-0.06 %) bytes
Max Waves: 36324 -> 36326 (0.01 %)
Instructions: 5073957 -> 5064164 (-0.19 %)

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Reviewed-by: Daniel Schürmann <daniel@schuermann.dev>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/merge_requests/2883>