Add alternative testcase of phi-opt-25.c that tests phiopt

Add alternative testcase of phi-opt-25.c that tests phiopt

Right now phi-opt-25.c has tests like `a ? func(a) : CST`
but if we add the simplifications to match.pd, then phi-opt-25.c
will no longer be testing phiopt to make sure these get optimized.
So this adds an alternative version which is designed to test
phiopt.

Committed as obvious after testing the testcase to make sure it does not
fail on x86_64-linux-gnu.

Thanks,
Andrew Pinski

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/phi-opt-25a.c: New test.