asm-generic updates for v6.1

This contains a series from Linus Walleij to unify the linux/io.h
interface by making the ia64, alpha, parisc and sparc include
asm-generic/io.h. All functions provided by the generic header are
now available to all drivers, but the architectures can still override
this. For the moment, mips and sh still don't include asm-generic/io.h
but provide a full set of functions themselves.

There are also a few minor cleanups unrelated to this.