[media] s5p-jpeg: Get rid of a warning

drivers/media/platform/s5p-jpeg/jpeg-hw-s5p.c: In function 's5p_jpeg_clear_int':
drivers/media/platform/s5p-jpeg/jpeg-hw-s5p.c:327:16: warning: variable 'reg' set but not used [-Wunused-but-set-variable]
  unsigned long reg;
                ^

Signed-off-by: Mauro Carvalho Chehab <m.chehab@samsung.com>