While ioremap() will happily map a physical address through the
P2 (uncached) segment when appropriate, iounmap() doesn't know how
to handle those mappings.

This patch makes iounmap() do the right thing, i.e. nothing, for
such mappings.
Signed-off-by: Haavard Skinnemoen <hskinnemoen@atmel.com>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>