ARM64: dts: Add Realtek RTD1295 and Zidoo X9S

Add initial device trees for the RTD1295 SoC and the Zidoo X9S TV box.

The CPUs lack the enable-method property because the vendor device tree
uses a custom "rtk-spin-table" method and "psci" did not appear to work.

The UARTs lack the interrupts properties because the vendor device tree
connects them to a custom interrupt controller. earlycon works without.

A list of memory reservations is adopted from v1.2.11 vendor device tree:
0x02200000 can be used for an initrd, 0x01b00000 is audio-related;
ion-related 0x02600000, 0x02c00000 and 0x11000000 are left out;
0x10000000 is used for sharing the U-Boot environment; others remain
to be investigated.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Andreas Färber <afaerber@suse.de>