match.pd: Fix indefinite recursion during exp-log transformations [PR118490]

match.pd: Fix indefinite recursion during exp-log transformations [PR118490]

This patch fixes the ICE caused when comparing log or exp of a constant with
another constant.

The transform is now restricted to cases where the resultant
log/exp (CST) can be constant folded.

Signed-off-by: Soumya AR <soumyaa@nvidia.com>
gcc/ChangeLog:

	PR target/118490
	* match.pd: Added ! to verify that log/exp (CST) can be constant folded.

gcc/testsuite/ChangeLog:

	PR target/118490
	* gcc.dg/pr118490.c: New test.