dax: Use non-exclusive wait in wait_entry_unlocked()

commit d8a706414af4827fc0b4b1c0c631c607351938b9 upstream.

get_unlocked_entry() uses an exclusive wait because it is guaranteed to
eventually obtain the lock and follow on with an unlock+wakeup cycle.
The wait_entry_unlocked() path does not have the same guarantee. Rather
than open-code an extra wakeup, just switch to a non-exclusive wait.

Cc: Matthew Wilcox <willy@infradead.org>
Reported-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>