can: raw: add locking for raw flags bitfield

In the Linux kernel, the following vulnerability has been resolved: can: raw: add locking for raw flags bitfield With commit 890e5198a6e5 ("can: raw: use bitfields to store flags in struct raw_sock") the formerly separate integer values have been integrated into a single bitfield. This led to a read-modify-write operation when changing a flag in raw_setsockopt() which now needs a locking to prevent concurrent access. Instead of adding a lock/unlock hell in each of the flag manipulations this patch introduces a wrapper for a new raw_setsockopt_locked() function analogue to the isotp_setsockopt[_locked]() approach in net/can/isotp.c [mkl: use Closes tag instead of Link]