This patch adds GPIO and IRQ support for the Diolan DLN-2 GPIO module.

Information about the USB protocol interface can be found in the
Programmer's Reference Manual [1], see section 2.9 for the GPIO
module commands and responses.

[1] https://www.diolan.com/downloads/dln-api-manual.pdfSigned-off-by: NDaniel Baluta <daniel.baluta@intel.com>
Signed-off-by: NOctavian Purdila <octavian.purdila@intel.com>
Acked-by: NLinus Walleij <linus.walleij@linaro.org>
Reviewed-by: NJohan Hovold <johan@kernel.org>
Signed-off-by: NLee Jones <lee.jones@linaro.org>