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.