This PR adds the drivers for Allwinner A64 PIO (Programmable I/O) and PinePhone LEDs (Red / Green / Blue).
The PIO Driver is based on the NuttX PIO Driver for Allwinner A10: [`arch/arm/src/a1x/a1x_pio.c`](https://github.com/apache/nuttx/blob/master/arch/arm/src/a1x/a1x_pio.c)
- `arch/arm64/src/a64/Make.defs`: Add PIO Driver to Makefile
- `boards/Kconfig`: Add `ARCH_HAVE_LEDS` to PinePhone
- `boards/arm64/a64/pinephone/src/pinephone.h`: Define PinePhone LEDs
- `boards/arm64/a64/pinephone/src/pinephone_boardinit.c`: Start Auto LEDs
- `boards/arm64/a64/pinephone/src/pinephone_bringup.c`: Start User LEDs
- `boards/arm64/a64/pinephone/src/Makefile`: Add LED Driver to Makefile
- `boards/arm64/a64/pinephone/configs/nsh/defconfig`: Add `CONFIG_USERLED` to `nsh` config
- `arch/arm64/src/a64/a64_pio.c`, `a64_pio.h`: Allwinner A64 PIO Driver
- `arch/arm64/src/a64/hardware/a64_memorymap.h`: PIO Memory Map
- `arch/arm64/src/a64/hardware/a64_pio.h`: PIO Definitions
- `boards/arm64/a64/pinephone/include/board.h`: Define PinePhone LEDs
- `boards/arm64/a64/pinephone/src/pinephone_autoleds.c`: Driver for Auto LEDs
- `boards/arm64/a64/pinephone/src/pinephone_userleds.c`: Driver for User LEDs
- `introduction/supported_platforms.rst`: Add Allwinner A64 as Supported Platform
- `platforms/arm/a64/boards/pinephone/index.rst`: Add PIO and LEDs to PinePhone
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