bus: add arm64 support to CCI driver

Update the PMU support in the CCI-400 driver to include arm64.

There are perf-events API differences between arm and arm64.
Add wrapper functions so that this driver will build for
either architecture. Some ARM-specific non-PMU functionality
is also compiled out when building for arm64.

Change-Id: Ic400156f31edbf957396f8fbb9239a4b896f2a54
Signed-off-by: Neil Leeder <nleeder@codeaurora.org>