i2c-iop3xx: add iomem annotation

Eliminate unnecessary casts and the following sparse warnings:

	drivers/i2c/busses/i2c-iop3xx.c:65:9: warning: incorrect type in argument 1 (different base types)
	drivers/i2c/busses/i2c-iop3xx.c:65:9:    expected void const volatile [noderef] <asn:2>*<noident>
	drivers/i2c/busses/i2c-iop3xx.c:65:9:    got unsigned int

	[ the previous warning is repeated 18 times ]

	drivers/i2c/busses/i2c-iop3xx.c:456:33: warning: cast removes address space of expression

Signed-off-by: Aaro Koskinen <aaro.koskinen@iki.fi>
Signed-off-by: Ben Dooks <ben-linux@fluff.org>