[ARM] 5364/1: allow flush_ioremap_region() to be used from modules

Without this, the pxa2xx-flash driver cannot be used as a module.

Reported-by: Chris Lawrence <chrisdl@netspace.net.au>

Signed-off-by: Nicolas Pitre <nico@marvell.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>