aco: remove redundant s_and exec after nir_op_inot

Totals from 22585 (15.04% of 150170) affected shaders: (GFX10.3)
VGPRs: 1474048 -> 1473904 (-0.01%)
CodeSize: 155238876 -> 155187688 (-0.03%); split: -0.06%, +0.03%
MaxWaves: 385086 -> 385122 (+0.01%)
Instrs: 29297735 -> 29284442 (-0.05%); split: -0.08%, +0.04%
Latency: 675841742 -> 675764151 (-0.01%); split: -0.02%, +0.01%
InvThroughput: 174859037 -> 174854796 (-0.00%); split: -0.01%, +0.01%
VClause: 479790 -> 479781 (-0.00%); split: -0.01%, +0.00%
SClause: 1106900 -> 1106615 (-0.03%); split: -0.03%, +0.01%
Copies: 1829037 -> 1828042 (-0.05%); split: -0.09%, +0.03%
Branches: 859971 -> 859967 (-0.00%); split: -0.00%, +0.00%
PreSGPRs: 1341850 -> 1342356 (+0.04%); split: -0.01%, +0.04%
PreVGPRs: 1327322 -> 1327034 (-0.02%)

Reviewed-by: Timur Kristóf <timur.kristof@gmail.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/11573>