bfd/dwarf2.c: fix assertion failure in comp_unit_hash_info

bfd/dwarf2.c: fix assertion failure in comp_unit_hash_info

stash_maybe_enable_info_hash_tables sets
stash->info_hash_status = STASH_INFO_HASH_ON;
regardless of the result of stash_maybe_update_info_hash_tables call. In
case it fails this results in repeated invocation of comp_unit_hash_info
for the same comp unit and assertion failure in this function.

Only set stash->info_hash_status = STASH_INFO_HASH_ON; when
stash_maybe_update_info_hash_tables is successful.

bfd/
2019-10-11  Max Filippov  <jcmvbkbc@gmail.com>

	* dwarf2.c (stash_maybe_enable_info_hash_tables): Only set
	stash->info_hash_status = STASH_INFO_HASH_ON when
	stash_maybe_update_info_hash_tables succeeds.