mtd: drivers/mtd/nand/sh_flctl.c: use resource_size()

Use resource_size().

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Acked-by: Yoshihiro Shimoda <shimoda.yoshihiro@renesas.com>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>