can: bcm: add missing rcu read protection for procfs content

In the Linux kernel, the following vulnerability has been resolved: can: bcm: add missing rcu read protection for procfs content When the procfs content is generated for a bcm_op which is in the process to be removed the procfs output might show unreliable data (UAF). As the removal of bcm_op's is already implemented with rcu handling this patch adds the missing rcu_read_lock() and makes sure the list entries are properly removed under rcu protection.