ARM: dts: sun8i: Add common dtsi file for NanoPi SBCs

This patch provides a common file for NanoPi M1 and Neo SBC.

Those have common features below.
  * UART0
  * 2 LEDs
  * USB host (EHCI3, OHCI3) and PHY
  * MicroSD
  * GPIO key switch

Cc: James Pettigrew <james@innovum.com.au>
Signed-off-by: Milo Kim <woogyom.kim@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>