pinctrl: sunxi: Add I2C pinmuxes

Where multiple options were available, the one matching board.c and the
device trees was chosen.

Pin lists and mux values were taken from the Linux drivers.

Signed-off-by: Samuel Holland <samuel@sholland.org>
[Andre: fixup H5 I2C1 pinmux]
Reviewed-by: Andre Przywara <andre.przywara@arm.com>
Signed-off-by: Andre Przywara <andre.przywara@arm.com>