cpus: denver: report CVE_2017_5715 mitigation to higher layers

This patch uses the 'declare_cpu_ops_wa' macro, to set the check function,
to report that Denver cores are mitigated.

Denver cores are vulnerable to this anomaly and require the mitigation to
be enabled always.

Change-Id: I1bb6eefdec8c01fb8b645e112f8d04d4bb8811ef
Signed-off-by: Varun Wadekar <vwadekar@nvidia.com>