[media] s5p-tv: Don't ignore return value of regulator_enable() in sii9234_drv.c

[media] s5p-tv: Don't ignore return value of regulator_enable() in sii9234_drv.c

This patch fixes following compilation warning:
  CC [M]  drivers/media/platform/s5p-tv/sii9234_drv.o
drivers/media/platform/s5p-tv/sii9234_drv.c: In function ‘sii9234_runtime_resume’:
drivers/media/platform/s5p-tv/sii9234_drv.c:252:18: warning: ignoring return
  value of ‘regulator_enable’, declared with attribute warn_unused_result

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>