USB: gadget: queue usb USB_CDC_GET_ENCAPSULATED_RESPONSE message

backport of 41566bcf

commit 0cf4f2de introduced a bug, which
prevents sending an USB_CDC_GET_ENCAPSULATED_RESPONSE message. This
breaks the RNDIS initialization (especially / only Windoze machines
dislike this behavior...).

Signed-off-by: Benedikt Spranger <b.spranger@linutronix.de>
Signed-off-by: Jan Altenberg <jan.altenberg@linutronix.de>
Acked-by: David Brownell <dbrownell@users.sourceforge.net>
Cc: Vernon Sauder <vernoninhand@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>