sparc64: Add kmemleak annotation to sun4v_build_virq()

The only reference we store to this memory is in the form of a
physical address, so kmemleak can't see it.

Add a kmemleak_not_leak() annotation.

It's probably useful to be able to look at a dump of these things
either via debugfs or similar, and thus we could at some point store
them in some kind of table and therefore get rid of this annotation.

Signed-off-by: David S. Miller <davem@davemloft.net>