pinctrl: sunxi: add support of R40 to A10 pinctrl driver

R40 is said to be an upgrade of A20, and its pin configuration is also
similar to A20 (and thus similar to A10).

Add support for R40 to the A10 pinctrl driver.

Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Reviewed-by: Chen-Yu Tsai <wens@csie.org>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>