ARM: sa11x0/assabet: ensure CS2 is configured appropriately

The CS2 region contains the Assabet board configuration and status
registers, which are 32-bit.  Unfortunately, some boot loaders do not
configure this region correctly, leaving it setup as a 16-bit region.
Fix this.

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