radeonsi: disable the TGSI merge registers pass

radeonsi: disable the TGSI merge registers pass

47109 shaders in 29632 tests
Totals:
SGPRS: 1917364 -> 1916620 (-0.04 %)
VGPRS: 1165802 -> 1165202 (-0.05 %)
Spilled SGPRs: 1880 -> 1843 (-1.97 %)
Spilled VGPRs: 70 -> 65 (-7.14 %)
Private memory VGPRs: 1184 -> 1184 (0.00 %)
Scratch size: 1312 -> 1308 (-0.30 %) dwords per thread
Code Size: 60211356 -> 60192268 (-0.03 %) bytes
LDS: 1077 -> 1077 (0.00 %) blocks
Max Waves: 428597 -> 428674 (0.02 %)
Wait states: 0 -> 0 (0.00 %)

Totals from affected shaders:
SGPRS: 238173 -> 237429 (-0.31 %)
VGPRS: 149556 -> 148956 (-0.40 %)
Spilled SGPRs: 1263 -> 1226 (-2.93 %)
Spilled VGPRs: 25 -> 20 (-20.00 %)
Private memory VGPRs: 0 -> 0 (0.00 %)
Scratch size: 20 -> 16 (-20.00 %) dwords per thread
Code Size: 10457904 -> 10438816 (-0.18 %) bytes
LDS: 50 -> 50 (0.00 %) blocks
Max Waves: 41283 -> 41360 (0.19 %)
Wait states: 0 -> 0 (0.00 %)

Signed-off-by: Samuel Pitoiset <samuel.pitoiset@gmail.com>
Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>
Reviewed-by: Marek Olšák <marek.olsak@amd.com>