MIPS: atomic: Fix comment describing atomic64_add_unless's return value.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Fixes: f24219b4e90cf70ec4a211b17fbabc725a0ddf3c
(cherry picked from commit f0a232cde7be18a207fd057dd79bbac8a0a45dec)
1 file changed