CRIS: assignment/is equal confusion

Somehow, the assignments of rw->lock got written as comparisons.
The effect probably was that the read-write spinlocks never locked.
However, since the locks are only used in CONFIG_SMP and SMP CRIS is
experimental, it has never been identified as a problem.

Signed-off-by: Roel Kluin <roel.kluin@gmail.com>
Acked-by: Jesper Nilsson <jesper.nilsson@axis.com>