ioremap() has special-case handling for the IS region, but inunmap() does not.
 So iounmap() generates a warning when a caller correctly performs an
ioremap()/iounmap() sequence.

Fix that by teaching iounmap() about the IS address range.
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>