usb: r8a66597-hcd: fix cannot detect low/full speed device

This controller can control "Transaction Translators", but
the hcd->has_tt is not set.
Since the commit d199c96d
("USB: prevent buggy from crashing the USB stack") has checked it,
the driver could not work the low/full speed device.

Signed-off-by: Yoshihiro Shimoda <yoshihiro.shimoda.uh@renesas.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>