[ARM] 4666/1: ixp4xx: fix sparse warnings in include/asm-arm/arch-ixp4xx/io.h

Don't lose __iomem in casts.  Use __force to cast __iomem addresses to
integers.  Use __force to cast u32 to __le32 and vice versa.

Signed-off-by: Pavel Roskin <proski@gnu.org>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>