DRM: armada: fix use of kfifo_put()

The kfifo_put() API changed in 498d319b

 (kfifo API type safety)
which now results in the wrong pointer being added to the kfifo ring,
which then causes an oops.  Fix this.

Cc: <stable@vger.kernel.org> # 3.13
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>