V4L/DVB (4492): [dvb_attach] dvb_frontend_detach fix

dvb_frontend_detach() used invalid config option CONFIG_DVB_DETACH,
so dvb_frontend_detach() did not call symbol_put_addr().
Replaced CONFIG_DVB_DETACH by CONFIG_DVB_CORE_ATTACH.

Signed-off-by: Oliver Endriss <o.endriss@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@infradead.org>