USB: m66592 and r8a66597 resource changes

Use the more common platform_get_resource() together with index instead
of depending on the resource name and platform_get_resource_by_name().
Replace the resource_len() implementation with resource_size().

Signed-off-by: Magnus Damm <damm@igel.co.jp>
Acked-by: Yoshihiro Shimoda <shimoda.yoshihiro@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>