add cpu native ordered io accessors ...

There are no generic native ordered io accessors. This sometimes
leads to

	v = in_be32(a);
	v = readl(a);

in generic drivers. Instead, use io accessors which are explicitely
native ordered.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>

introduce io.h ...

To allow for some generic io accessors introduce io.h and use
this instead of asm/io.h throughout the tree.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>