Patch from Lennert Buytenhek

This patch makes the ixp2000 port use section mappings for on-chip
registers.  This has two advantages:
1. It saves some TLB entries.
2. It enables us to work around ixp2400 erratum #66, for which the
   suggested (and only) fix involves mapping all on-chip registers
   using XCB=101 instead of XCB=000.
This patch was derived from an older patch for the same erratum
(ARM patch ID 2265/1), made by Deepak Saxena.
Note that this patch does not actually constitute a workaround for
erratum #66, it merely lays the foundation for such a workaround.

Signed-off-by: Lennert BuytenhekSigned-off-by: Deepak Saxena
Signed-off-by: Russell King