Fix overactive sanity check in profile_count::to_sreal_scale

Fix overactive sanity check in profile_count::to_sreal_scale

As discussed in the PR log, profile_count::to_cgraph_frequency was originally
intended to work across function boundary and has some extra logic and sanity
check for that.  It is used only within single function and with current
API it can not really work well globally, so this patch synchronizes its
implementation with probability_in which does similar job but to determine
relative probability.

gcc/ChangeLog:

2023-03-14  Jan Hubicka  <hubicka@ucw.cz>

	PR tree-optimization/106896
	* profile-count.cc (profile_count::to_sreal_scale): Synchronize
	implementatoin with probability_in; avoid some asserts.