ARM: cache-l2x0: update workaround for PL310 errata 727915

ARM errata 727915 for PL310 has been updated to include a new
workaround required for PL310 r2p0 for l2x0_flush_all, which also
affects l2x0_clean_all in my testing.  For r2p0, clean or flush
each set/way individually.  For r3p0 or greater, use the debug
register for cleaning and flushing.

Requires exporting the cache_id, sets and ways detected in the
init function for later use.

Change-Id: I215055cbe5dc7e4e8184fb2befc4aff672ef0a12
Signed-off-by: Colin Cross <ccross@android.com>