ARM: l2c: implement L2C-310 erratum 588369 as a method override

Implement L2C-310 erratum 588369 by overriding the invalidate range
and flush range methods in the outer_cache operations structure.
This allows us to sensibly contain the erratum code in one place
without affecting other locations/implemetations.

Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>