We have one caller that cycles the rcu lock solely for this call
(via target_rw_devs()), and we'd like to add another. Simplify
things by pushing the rcu lock down into bch2_target_to_mask(),
similar to how bch2_dev_in_target() works.
Signed-off-by: Brian Foster <bfoster@redhat.com>
Signed-off-by: Kent Overstreet <kent.overstreet@linux.dev>