Set dwarf2 stash pointer earlier

Set dwarf2 stash pointer earlier

This fixes a memory leak in the vanishingly rare cases (found by
fuzzers of course) when something goes wrong in the save_section_vma,
htab_create_alloc or alloc_trie_leaf calls before *pinfo is written.
If *pinfo is not written, _bfd_dwarf2_cleanup_debug_info won't be able
to free that memory.

	* dwarf2.c (_bfd_dwarf2_slurp_debug_info): Save stash pointer
	on setting up stash.