cacheinfo: Use cache identifiers to check if the caches are shared if available

The cache identifiers is an optional property on most of the platforms.
The presence of one must be indicated by the CACHE_ID valid bit in the
attributes.

We can use the cache identifiers provided by the firmware to check if
any two cpus share the same cache instead of relying on the fw_token
generated and set in the OS.

Tested-by: Ionela Voinescu <ionela.voinescu@arm.com>
Signed-off-by: Sudeep Holla <sudeep.holla@arm.com>