predict: Don't emit -Wsuggest-attribute=cold warning for functions which...

predict: Don't emit -Wsuggest-attribute=cold warning for functions which already have that attribute [PR105685]

In the following testcase, we predict baz to have cold
entry regardless of the user supplied attribute (as it call
unconditionally a cold function), but still issue
a -Wsuggest-attribute=cold warning despite it having that attribute
already.

The following patch avoids that.

2023-03-26  Jakub Jelinek  <jakub@redhat.com>

	PR ipa/105685
	* predict.cc (compute_function_frequency): Don't call
	warn_function_cold if function already has cold attribute.

	* c-c++-common/cold-2.c: New test.