[MPS] LogSoftmax numerical stability (#95091)
Fixes #94043
Calculations are now consistent with numericaly stable formula and CPU:
$LogSoftmax(X, \dim) = X - \max(X, \dim) - \log(sum(X - \max(X, \dim), \dim))$
@malfet
Pull Request resolved: https://github.com/pytorch/pytorch/pull/95091
Approved by: https://github.com/malfet, https://github.com/kulinseth
