arm64: allwinner: A100: add the basical Allwinner A100 DTSI file

Allwinner A100 is a new SoC with Cortex-A53 cores, this commit adds
the basical DTSI file of it, including the clock, i2c, pins, sid, ths,
nmi, and UART support.

Signed-off-by: Yangtao Li <frank@allwinnertech.com>
Signed-off-by: Maxime Ripard <maxime@cerno.tech>
Link: https://lore.kernel.org/r/815a458de74b79eb649972de786e647be3846424.1595572867.git.frank@allwinnertech.com