profiling: fix streaming of TOPN counters

libgcc/ChangeLog:

	PR gcov-profile/99105
	* libgcov-driver.c (write_top_counters): Rename to ...
	(write_topn_counters): ... this.
	(write_one_data): Pre-allocate buffer for number of items
	in the corresponding linked lists.
	* libgcov.h (malloc_mmap): New function.
	(allocate_gcov_kvp): Use it.

gcc/testsuite/ChangeLog:

	PR gcov-profile/99105
	* gcc.dg/tree-prof/indir-call-prof-malloc.c: Use profile
	correction as the wrapped malloc is called one more time
	from libgcov.
	* gcc.dg/tree-prof/pr97461.c: Likewise.