bt8xx: fix memory leak

[ Upstream commit 6792eb0cf9310ec240b7e7c9bfa86dff4c758c68 ]

If dvb_attach() fails then we were just printing an error message and
exiting but the memory allocated to state was not released.

Signed-off-by: Sudip Mukherjee <sudip.mukherjee@codethink.co.uk>
Signed-off-by: Hans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>
Signed-off-by: Sasha Levin <alexander.levin@verizon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>