Several attributes in the ieee802154_context struct may potentially be
accessed from different threads and/or ISR context. Only some of these
attributes were properly guarded against race conditions.
This may not have been to problematic in the past but as other changes
in this PR introduce additional attributes and mutate several attributes
in a single atomic transaction, leaving such changes unprotected seems
dangerous.
This change therefore introduces systematic locking of the
ieee802154_context structure.
Signed-off-by: Florian Grandel <jerico.dev@gmail.com>