[ARM] 3257/1: ixp2000: map in scratch and sram

Patch from Lennert Buytenhek

For the ixp2000 netdev driver, we need to map in a chunk of SRAM (to
store the transmit and receive descriptors) and the scratch get/put
area (so that we can use the scratchpad rings in the cpu for managing
the descriptors.)  These are the final two mappings needed for the
netdev driver and the last missing piece for the driver in mainline
to work.

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