When merging A20 pinctrl support to A10 pinctrl driver, the I2C function
of PI3 is wrongly written as "i2c3" (it should be "i2c4").

Fix this typo.

Fixes: cad4e209 ("pinctrl: sunxi: add support of R40 to A10 pinctrl driver")
Reported-by: Mark Kettenis <mark.kettenis@xs4all.nl>
Signed-off-by: Icenowy Zheng <icenowy@aosc.io>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>