Fix a bug introduced in commit 9cf5b0ea3a:
function rfcomm_recv_ua calls rfcomm_session_put without checking that
the session is not referenced by some DLC. If the session is freed, that
DLC would refer to deallocated memory, causing an oops later, as shown
in this bug report: https://bugzilla.kernel.org/show_bug.cgi?id=15994
Signed-off-by: Lukas Turek <8an@praha12.net>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>