[media] s5p-fimc: convert struct spinlock to spinlock_t

spinlock_t should always be used.
Could not get this to build with allmodconfig:
mcgrof@frijol ~/linux-next (git::(no branch))$ make C=1 M=drivers/media/platform/s5p-fimc/
  WARNING: Symbol version dump /home/mcgrof/linux-next/Module.symvers
           is missing; modules will have no dependencies and modversions.
  LD      drivers/media/platform/s5p-fimc/built-in.o
  Building modules, stage 2.
  MODPOST 0 modules

Reported-by: Hauke Mehrtens <hauke@hauke-m.de>
Signed-off-by: Luis R. Rodriguez <mcgrof@do-not-panic.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/platform/s5p-fimc/mipi-csis.c

@@ -187,7 +187,7 @@ struct csis_state {
 	const struct csis_pix_format *csis_fmt;
 	struct v4l2_mbus_framefmt format;
 
-	struct spinlock slock;
+	spinlock_t slock;
 	struct csis_pktbuf pkt_buf;
 	struct s5pcsis_event events[S5PCSIS_NUM_EVENTS];
 };