pinctrl: sunxi: Add external interrupt functions

The A10 and A13 has a few pins that can be muxed into a particular
function that can be used as an interrupt source. Add the available
pins for such functions to the A10 and A13 description array.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>