microblaze: Reversed logic in futex cmpxchg

futex_atomic_cmpxchg_inatomic exchanged if the values were
unequal rather than equal. This caused incorrect behavior
of robust futexes.

Signed-off-by: Kirk Meyer <kirk.meyer@sencore.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>