ia64: If the compiler supports it, use attribute (model (small)) to

ia64: If the compiler supports it, use attribute (model (small)) to
	tell the compiler that per-CPU variables can be addressed
	with "addl".

	On the simulator kernel, this saves about 2776 bytes in the
	kernel image.  On a zx1 kernel, it saves about 5593 bytes.
	As per-CPU variables are used more, these savings will
	increase, of course.