gpio: xra1403: Add EXAR XRA1403 SPI GPIO expander driver

This driver support basic XRA1403 functionalities:
    - set gpio direction
    - get gpio direction
    - set gpio high/low
    - get gpio status

Signed-off-by: Nandor Han <nandor.han@ge.com>
Signed-off-by: Semi Malinen <semi.malinen@ge.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>