LinuxKPI: add rcu_dereference_check()

Add a define for rcu_dereference_check() to rcu_dereference_protected()
which ignores the check argument. Our lockdep compat implementation
for use cases found in iwlwifi would return 1 anyway.

Sponsored by: The FreeBSD Foundation
MFC after: 2 weeks
Reviewed by: hselasky
Differential Revision: https://reviews.freebsd.org/D30436