Enabling CONFIG_DEBUG_ATOMIC_SLEEP has shown that some rfcomm functions
acquiring spinlocks call sleeping locks further in the chain.  Converting
the offending spinlocks into mutexes makes sleeping safe.
Signed-off-by: NLibor Pechacek <lpechacek@suse.cz>
Signed-off-by: NMarcel Holtmann <marcel@holtmann.org>