pinctrl: sunxi: Declare the number of interrupt banks in the descriptor

Declare in the description structure associated to the compatible the number of
interrupt banks the device has. For now, we're not doing anything with it.

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