nir/algebraic: disable rcp(exp(a)) -> exp(-a) optimization

Fixes a Borderlands 3 precision issue with the expression:
floor(71 / exp(-3.3219280242919921875)).

fossil-db (navi21):
Totals from 1055 (0.78% of 135636) affected shaders:
Instrs: 1175831 -> 1178025 (+0.19%); split: -0.00%, +0.19%
CodeSize: 6373172 -> 6373148 (-0.00%); split: -0.00%, +0.00%
Latency: 28242666 -> 28263222 (+0.07%); split: -0.00%, +0.07%
InvThroughput: 4682055 -> 4686146 (+0.09%)
SClause: 50943 -> 50954 (+0.02%); split: -0.00%, +0.03%
Copies: 60667 -> 60657 (-0.02%); split: -0.04%, +0.02%

Signed-off-by: Rhys Perry <pendingchaos02@gmail.com>
Closes: mesa/mesa#7752