ieee1394: raw1394: Do not leak memory on failed trylock.

Do not leak the allocated memory in case the mutex_trylock() failed
to acquire the lock.

Signed-off-by: Michael Buesch <mb@bu3sch.de>

This bug does not happen in practice:  All raw1394 clients use
libraw1394, and accesses to a libraw1394 handle need to be serialized
by the client.  This is documented in libraw1394's API reference.

Signed-off-by: Stefan Richter <stefanr@s5r6.in-berlin.de>