dt-bindings: arm: sunxi: document LicheePi Nano name

dt-bindings: arm: sunxi: document LicheePi Nano name

The top level LicheePi Nano compatible name was never documented in the
bindings, so add the currently used string.

As for the manufacturer name, Samuel reports:
==========
From what  I can tell, "Lichee Pi Nano" [1][2] is the original board, and the
"Sipeed Lichee Nano" [3] is a newer batch by some of the same people [4].

Other than the silkscreen and the addition of the resistive touchscreen IC, the
boards look identical. And in fact I was able to find an intermediate version of
the schematic [5] that uses the old styling but includes the touchscreen IC.
==========

[1]: https://licheepizero.us/
[2]: http://nano.lichee.pro/
[3]: https://wiki.sipeed.com/hardware/en/lichee/Nano/Nano.html
[4]: see e.g. http://bbs.lichee.pro/
[5]:
https://github.com/hongxuyao/F1C100s_with_Keil_RTX4_emWin5/blob/spl-separated/doc/lichee-nano/lichee_nano-Schematic.pdf

Signed-off-by: Andre Przywara <andre.przywara@arm.com>
Reviewed-by: Samuel Holland <samuel@sholland.org>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Jernej Skrabec <jernej.skrabec@gmail.com>
Link: https://lore.kernel.org/r/20220317162349.739636-5-andre.przywara@arm.com