mtd: drivers/mtd/nand/s3c2410.c: use resource_size()

Use resource_size().

Signed-off-by: H Hartley Sweeten <hsweeten@visionengravers.com>
Cc: Ben Dooks <ben-linux@fluff.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>