ARM: dts: sun8i: h3: Add eMMC for NanoPi M1 Plus

The NanoPi-M1-Plus have a 8GB eMMC, add a node for it.
This eMMC is always powered with 3.3V.

Signed-off-by: Emmanuel Vadot <manu@freebsd.org>
Signed-off-by: Maxime Ripard <maxime.ripard@bootlin.com>
[wens@csie.org: Fixed "mmc2_8bits_pins" label typo; added subject prefixes]
Signed-off-by: Chen-Yu Tsai <wens@csie.org>