Scale up auto-profile counts

Scale up auto-profile counts

This patch makes auto-profile counts to scale up when the train run has
too small maximal count.  This still happens on moderately sized train runs
such as SPEC2017 ref datasets and helps to avoid rounding errors in cases
where number of samples is small.

gcc/ChangeLog:

	* auto-profile.cc (autofdo::afdo_count_scale): New.
	(autofdo_source_profile::update_inlined_ind_target): Scale
	counts.
	(autofdo_source_profile::read): Set scale and dump
	statistics.
	(afdo_indirect_call): Scale.
	(afdo_set_bb_count): Scale.
	(afdo_find_equiv_class): Fix dumps.
	(afdo_annotate_cfg): Scale.