match: Improve `(a != b) ? (a + b) : (2 * a)` pattern [PR19832]

match: Improve `(a != b) ? (a + b) : (2 * a)` pattern [PR19832]

In the testcase provided, we would match f_plus but not g_plus
due to a missing `:c` on the plus operator. This fixes the oversight
there.

Note this was noted in https://github.com/llvm/llvm-project/issues/76318 .

Committed as obvious after bootstrap/test on x86_64-linux-gnu.

	PR tree-optimization/19832

gcc/ChangeLog:

	* match.pd (`(a != b) ? (a + b) : (2 * a)`): Add `:c`
	on the plus operator.

gcc/testsuite/ChangeLog:

	* gcc.dg/tree-ssa/phi-opt-same-2.c: New test.

Signed-off-by: Andrew Pinski <quic_apinski@quicinc.com>