Bluetooth: Revert to mutexes from RCU list

Usage of RCU list looks not reasonalbe for a number of reasons:
our code sleep and we had to use socket spinlocks. Most parts
of code are updaters thus there is little sense to use RCU.

Signed-off-by: Andrei Emeltchenko <[email protected]>
Reviewed-by: Ulisses Furquim <[email protected]>
Acked-by: Gustavo F. Padovan <[email protected]>
Signed-off-by: Johan Hedberg <[email protected]>

Author: finikorg