radv: run the EarlyCSEMemSSA LLVM pass

radv: run the EarlyCSEMemSSA LLVM pass

It's recommended by the instruction combining pass, and
RadeonSI also runs it.

This pass used to segfault with one shader of F12017 in the
past, but it no longer crashes. Maybe the LLVM IR generated
by RADV has changed.

Polaris10:
Totals from affected shaders:
SGPRS: 441352 -> 441648 (0.07 %)
VGPRS: 310888 -> 300784 (-3.25 %)
Spilled SGPRs: 13576 -> 12983 (-4.37 %)
Code Size: 22560328 -> 22420544 (-0.62 %) bytes
Max Waves: 40755 -> 41366 (1.50 %)

Vega10:
Totals from affected shaders:
SGPRS: 442848 -> 442000 (-0.19 %)
VGPRS: 310396 -> 300460 (-3.20 %)
Spilled SGPRs: 13708 -> 12906 (-5.85 %)
Code Size: 22479428 -> 22336216 (-0.64 %) bytes
Max Waves: 45783 -> 46506 (1.58 %)

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Bas Nieuwenhuizen <bas@basnieuwenhuizen.nl>