USB: Add usb_endpoint_xfer_control to usb.h

Added a function to check if an endpoint is a control endpoint.
There were similar functions for bulk, interrupt, and isoc,
but not for control endpoints.

Signed-off-by: Sarah Bailey <saharabeara@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>