This PR adds the driver for TCON0 (Timing Controller) on Allwinner A64 SoC. The TCON0 Driver will be used by the upcoming Display Driver for PINE64 PinePhone.
`arch/arm64/src/a64/Kconfig`: Added the Kconfig option for "A64 Peripheral Selection > TCON0" (`CONFIG_A64_TCON0`), which enables the TCON0 Driver
`arch/arm64/src/a64/hardware/a64_memorymap.h`: Added the Base Address for TCON0
`arch/arm64/src/a64/Make.defs`: Added the TCON0 Driver to the Makefile
`arch/arm64/src/a64/a64_tcon0.c`, `a64_tcon0.h`: TCON0 Driver for Allwinner A64
`platforms/arm/a64/boards/pinephone/index.rst`: Added TCON0 as supported peripheral for PinePhone
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