[media] s5c73m3: Do not ignore errors from regulator_enable()

This fixes following compilation warning:
drivers/media/i2c/s5c73m3/s5c73m3-core.c: In function ‘__s5c73m3_power_off’:
drivers/media/i2c/s5c73m3/s5c73m3-core.c:1389:19: 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>