[PATCH] w83792d: Add missing data access locks

Add missing data lock in w83792d driver to avoid unexpected
data change.

Signed-off-by: Yuan Mu <ymu@winbond.com.tw>
Signed-off-by: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>