make_corefile_notes: have caller free returned memory

make_corefile_notes: have caller free returned memory

The various make_corefile_notes implementations for gdbarch as well as target
currently make an xfree cleanup on the data they return.  This causes problems
when trying to put a TRY_CATCH around the make_corefile_notes call.
Specifically, we get a stale cleanup error in restore_my_cleanups.

Omit the make_cleanup and have the caller free the memory.

gdb/
	* fbsd-nat.c (fbsd_make_corefile_notes): Remove make_cleanup call.
	* gcore.c (write_gcore_file): Free memory returned from
	make_corefile_notes.
	* linux-tdep.c (linux_make_corefile_notes): Remove make_cleanup call.
	* procfs.c (procfs_make_note_section): Remove make_cleanup call.