This PR adds the driver for Display Engine 2.0 on Allwinner A64 SoC. The Display Engine Driver will be called by the upcoming LCD Driver for PINE64 PinePhone.
`arch/arm64/src/a64/Kconfig`: Added the Kconfig option for "A64 Peripheral Selection > DE" (`CONFIG_A64_DE`), which enables the Display Engine Driver
`arch/arm64/src/a64/hardware/a64_memorymap.h`: Added the Base Address for Display Engine
`arch/arm64/src/a64/Make.defs`: Added the Display Engine Driver to the Makefile
`boards/arm64/a64/pinephone/configs/nsh/defconfig`: Removed Scheduler Debug Info (`CONFIG_DEBUG_SCHED_INFO`) from the PinePhone Board Config, because it garbles the Console Output.
`arch/arm64/src/a64/a64_de.c`, `a64_de.h`: Display Engine Driver for Allwinner A64
`platforms/arm/a64/boards/pinephone/index.rst`: Added Display Engine as supported peripheral for PinePhone