ia64: use asm-generic/io.h

asm-generic/io.h provides a generic implementation of all I/O accessors,
which the architectures can override.

Since ia64 does not provide readsl/writesl etc, any driver using those
fails to build, and including asm-generic/io.h will provide the
missing interfaces, as well as any other future interfaces that get
added there. We need to #define a couple of symbols to themselves
in the ia64 to ensure that we use the ia64 specific version of those
rather than the generic one.

There should be no other effect than adding {read,write}s{b,w,l}()
as well as {in,out}s{b,w,l}_p(), which were also not provided
by ia64 but are provided by the generic header for historic reasons.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Tested-by: Boris Brezillon <boris.brezillon@bootlin.com>
Signed-off-by: Miquel Raynal <miquel.raynal@bootlin.com>