Move conn_unlock() after the data event handling in can_callback()
and udp_callback(). Previously, the connection lock was released
immediately after devif_conn_event(), leaving the subsequent
can_data_event()/net_dataevent() and read-ahead buffer operations
unprotected. This could lead to a race condition where another
context modifies the connection state while data is being stored.
Hold the lock until the entire callback processing is complete to
ensure thread safety.
Signed-off-by: zhanghongyu <zhanghongyu@xiaomi.com>