If bailing out because there is nothing to receive in rp_do_receive(),
tty_ldisc_deref is not called.  Failure to do so increases the ref count
and causes release_dev() to hang since it can't get the ref count to 0.
Signed-off-by: NMichal Ostrowski <mostrows@watson.ibm.com>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>