ARM: dts: Add Raspberry Pi Zero 2 W

The Raspberry Pi Zero 2 W mostly bases on the Raspberry Pi Zero W with
the following differences:
* Broadcom BCM2710A1, quad-core 64-bit SoC @ 1 GHz
* Synaptics BCM43436 (reported as BCM43430B0) IEEE 802.11b/g/n wireless LAN

Contrary to the Raspberry Pi 3 boards there is no GPIO expander.

Signed-off-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>