Patch from Lennert Buytenhek

Add a mapping for the ixp2400 and ixp2800 msf unit.  The msf is the
ixp2000's 'media and switch fabric' unit, which handles the networking
part of the chip.
Signed-off-by: Lennert Buytenhek <buytenh@wantstofly.org>
Signed-off-by: Deepak Saxena
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>