bitops: use try_cmpxchg in set_mask_bits and bit_clear_unless

Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in
set_mask_bits and bit_clear_unless.  x86 CMPXCHG instruction returns
success in ZF flag, so this change saves a compare after cmpxchg (and
related move instruction in front of cmpxchg).

Also, try_cmpxchg implicitly assigns old *ptr value to "old" when cmpxchg
fails, enabling further code simplifications.

Link: https://lkml.kernel.org/r/20220822143851.3290-1-ubizjak@gmail.com


Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>