[ARM] 3526/1: ioremap should use vunmap instead of vfree on ARM

Patch from Catalin Marinas

This patch modifies the __ioremap_pfn and __iounmap functions in
arch/arm/mm/ioremap.c to use vunmap instead of vfree.

Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>