counter: 104-quad-8: Add lock guards - generic interface

Add lock protection from race conditions to 104-quad-8 counter driver
generic interface code changes. Mutex calls used for protection.

Fixes: f1d8a07 ("counter: 104-quad-8: Add Generic Counter interface support")

Signed-off-by: Syed Nayyar Waris <[email protected]>
Signed-off-by: William Breathitt Gray <[email protected]>
Signed-off-by: Jonathan Cameron <[email protected]>

Author: Syed Nayyar Waris