usb: cp210x: Corrected USB request type definitions

The original request types in the cp210x driver are labled as "DEVICE_TO_HOST" and
"HOST_TO_DEVICE" but the actual bit definition corresponds to a request to the
interface. This has been corrected, and the actual definition for the device
requests have been added.

Signed-off-by: Preston Fick <preston.fick@silabs.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>