[IA64] move ioremap/ioremap_nocache under __KERNEL__

I noticed these are declared extern outside of __KERNEL__, but surely
they wouldn't be available to userland since they're defined in
ioremap.c.  Am I missing something here?

If I'm right about this, then there's probably a good deal of other
stuff in io.h that could move inside __KERNEL__, but at least this is
a start.

Signed-off-by: Aron Griffis <aron@hp.com>
Signed-off-by: Tony Luck <tony.luck@intel.com>