ARM: sun5i: chip: Add optional buses

The I2C1 and SPI2 buses are exposed on the CHIP headers, and are not
explicitly dedicated to anything.

Add them to the DTS with the muxing already set, but keep them disabled.

Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Acked-by: Chen-Yu Tsai <wens@csie.org>