res can be one of several resources, as this variable is re-used several
times during probe.  This can cause the wrong resource parameters to be
passed to release_mem_region().

Get the original memory resource before calling release_mem_region().
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
Acked-by: Tony Lindgren <tony@atomide.com>
Signed-off-by: Chris Ball <cjb@laptop.org>