ARM: 7716/1: bcm281xx: Add L2 support for Rev A2 chips

Rev A2 SoCs have an unorthodox memory re-mapping and this needs
to be reflected in the cache operations.
This patch adds new outer cache functions for the l2x0 driver
to support this SoC revision. It also adds a new compatible
value for the cache to enable this functionality.

Updates from V1:
- remove section 1 altogether and note that in comments
- simplify section selection caused by section 1 removal
- BUG_ON just in case section 1 shows up

Signed-off-by: Christian Daudt <csd@broadcom.com>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Acked-by: Olof Johansson <olof@lixom.net>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>