USB: ohci-s3c2410: use resource_size()

This patch uses the resource_size help function instead of
manually calculating the resource size. It can reduce the chance
of introducing off-by-one errors.

Signed-off-by: Jingoo Han <jg1.han@samsung.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>