Fix incorrect loop exit edge probability [PR103270]

r12-4526 cancelled jump thread path rotates loop. It exposes a issue in
profile-estimate when predict_extra_loop_exits, outer loop's exit edge
is marked as inner loop's extra loop exit and set with incorrect
prediction, then a hot inner loop will become cold loop finally through
optimizations, this patch add loop check when searching extra exit edges
to avoid unexpected predict_edge from predict_paths_for_bb.

Regression tested on P8LE.

gcc/ChangeLog:

2021-12-21  Xionghu Luo  <luoxhu@linux.ibm.com>

	PR middle-end/103270
	* predict.c (predict_extra_loop_exits): Add loop parameter.
	(predict_loops): Call with loop argument.

gcc/testsuite/ChangeLog:

2021-12-21  Xionghu Luo  <luoxhu@linux.ibm.com>

	PR middle-end/103270
	* gcc.dg/pr103270.c: New test.