arm64: dts: qcom: Add SDM660 SoC support

arm64: dts: qcom: Add SDM660 SoC support

Initial device tree support for Qualcomm SDM660 SoC.

SDM660 is based off MSM8998 and uses some of its drivers.
SDM630/636 are based off SDM660 SoC and they are pin
and software compatible.

The device tree is based on the CAF 4.4 kernel tree.

Features:
 * CPU nodes
 * Timer nodes
 * Interrupt controller
 * Global Clock Controller
 * Top Level Mode Multiplexer (pin controller)
 * UART node

This is inspired by and based on the work of Craig Tatlor in
https://patchwork.kernel.org/patch/10563667/

Signed-off-by: Craig Tatlor <ctatlor97@gmail.com>
Signed-off-by: Alexey Minnekhanov <alexey.min@gmail.com>
Link: https://lore.kernel.org/r/20200417012630.222352-3-alexey.min@gmail.com
Signed-off-by: Bjorn Andersson <bjorn.andersson@linaro.org>