mfd: kempld-core: Use resource_size function on resource object

drivers/mfd/kempld-core.c:461:13-16: WARNING: Suspicious code. resource_size is maybe missing with ioport

Generated by: scripts/coccinelle/api/resource_size.cocci

Signed-off-by: Vasyl Gomonovych <gomonovych@gmail.com>
Signed-off-by: Lee Jones <lee.jones@linaro.org>