V4L/DVB (13963): siano, fix memory leak

Stanse found a memory leak in smscore_gpio_configure. buffer is not
freed/assigned on all paths. Fix that.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>