USB: dummy-hcd: use usb_urb_dir_in instead of usb_pipein

USB: dummy-hcd: use usb_urb_dir_in instead of usb_pipein

Commit 374fbe6ba189 ("USB: add direction bit to urb->transfer_flags") has
added a usb_urb_dir_in() helper function that can be used to determine
the direction of the URB. With that patch USB_DIR_IN control requests with
wLength == 0 are considered out requests by real USB HCDs. This patch
changes dummy-hcd to use the usb_urb_dir_in() helper to match that
behavior.

Signed-off-by: Andrey Konovalov <andreyknvl@google.com>
Link: https://lore.kernel.org/r/4ae9e68ebca02f08a93ac61fe065057c9a01f0a8.1571667489.git.andreyknvl@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>