[media] s5p-jpeg: 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-jpeg
  WARNING: Symbol version dump /home/mcgrof/linux-next/Module.symvers
           is missing; modules will have no dependencies and modversions.
  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-jpeg/jpeg-core.h

@@ -62,7 +62,7 @@
  */
 struct s5p_jpeg {
 	struct mutex		lock;
-	struct spinlock		slock;
+	spinlock_t		slock;
 
 	struct v4l2_device	v4l2_dev;
 	struct video_device	*vfd_encoder;