iommu_init() and iounit_init() are never called for sun4, but that's not
enough - these calls should be ifdefed out since the functions in question
simply do not exist for CONFIG_SUN4 kernel.

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>