sunxi: i2c: Add support for DM I2C

This commit adds support for DM I2C on sunxi platform. It can coexist
with old style sunxi I2C driver, because it is still used in SPL and
by some SoCs.

Because sunxi platform doesn't yet support DM clk, reset and pinctrl
driver, workaround is needed to enable clocks and set resets and
pinctrls. This is done by calling i2c_init_board() in board_init().
This means that CONFIG_I2Cx_ENABLE options needs to be correctly set
in order to use needed I2C controller.

Commit is based on the previous patch made by Philipp Tomsich

Signed-off-by: Jernej Skrabec <jernej.skrabec@siol.net>
Reviewed-by: Heiko Schocher <hs@denx.de>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>