V4L/DVB: radio-si4713: Release i2c adapter in driver cleanup paths

Call to i2c_put_adapter was missing in radio_si4713_pdriver_probe and
radio_si4713_pdriver_remove.

Signed-off-by: Jarkko Nikula <jhnikula@gmail.com>
Acked-by: Eduardo Valentin <eduardo.valentin@nokia.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>