Now that we try to create ffma from the beginning and are less reliant on
inexact optimizations, we can enable this with much less regressions on
GFX10.3.

fossil-db (GFX10.3):
Totals from 53274 (36.42% of 146267) affected shaders:
VGPRs: 1979216 -> 1975944 (-0.17%); split: -0.67%, +0.50%
SpillSGPRs: 1462 -> 1446 (-1.09%)
CodeSize: 77389256 -> 79231200 (+2.38%); split: -0.06%, +2.44%
MaxWaves: 1418040 -> 1419400 (+0.10%); split: +0.34%, -0.24%
Instrs: 15015014 -> 15453979 (+2.92%); split: -0.14%, +3.06%
Latency: 89229974 -> 89562172 (+0.37%); split: -0.76%, +1.13%
InvThroughput: 15488878 -> 15990928 (+3.24%); split: -0.25%, +3.50%

fossil-db (GFX10):
Totals from 12563 (8.59% of 146267) affected shaders:
VGPRs: 532880 -> 532200 (-0.13%); split: -0.42%, +0.29%
SpillSGPRs: 1462 -> 1446 (-1.09%)
CodeSize: 30125368 -> 30275508 (+0.50%); split: -0.06%, +0.56%
MaxWaves: 327120 -> 327484 (+0.11%); split: +0.31%, -0.20%
Instrs: 5783753 -> 5834581 (+0.88%); split: -0.02%, +0.89%
Latency: 29271625 -> 29349407 (+0.27%); split: -0.14%, +0.41%
InvThroughput: 6801730 -> 6855695 (+0.79%); split: -0.04%, +0.83%

fossil-db (GFX9):
Totals from 12563 (8.58% of 146401) affected shaders:
SGPRs: 717840 -> 717888 (+0.01%); split: -0.16%, +0.16%
VGPRs: 531464 -> 531892 (+0.08%); split: -0.23%, +0.31%
SpillSGPRs: 1770 -> 1750 (-1.13%)
CodeSize: 27658752 -> 27814028 (+0.56%); split: -0.05%, +0.61%
MaxWaves: 81149 -> 81224 (+0.09%); split: +0.24%, -0.14%
Instrs: 5489024 -> 5537939 (+0.89%); split: -0.02%, +0.91%
Latency: 43480815 -> 43657720 (+0.41%); split: -0.08%, +0.49%
InvThroughput: 19853380 -> 20017416 (+0.83%); split: -0.04%, +0.87%

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>