io-mapping: Fix the address space annotations

Fixes a bunch of sparse warnings in io-mapping.h because of the
inconsistent __iomem usage.

Signed-off-by: Francisco Jerez <currojerez@riseup.net>
LKML-Reference: <1283633804-11749-2-git-send-email-currojerez@riseup.net>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>