aco: don't assume that v_interp_mov_f32 flushes denorms

Foz-DB Navi21:
Totals from 3 (0.00% of 79789) affected shaders:
Instrs: 1708 -> 1722 (+0.82%)
CodeSize: 9416 -> 9460 (+0.47%)
Latency: 12094 -> 12371 (+2.29%); split: -0.02%, +2.31%
InvThroughput: 1967 -> 1992 (+1.27%)
Copies: 105 -> 106 (+0.95%)
PreVGPRs: 131 -> 132 (+0.76%)
VALU: 1155 -> 1169 (+1.21%)

Reviewed-by: Rhys Perry <pendingchaos02@gmail.com>
Part-of: <!33974>