ARM: renesas: Add R8A779A0 V3U Falcon board code

Add board code for the R8A779A0 V3U Falcon board.

Signed-off-by: Hai Pham <hai.pham.ud@renesas.com>
Signed-off-by: Marek Vasut <marek.vasut+renesas@gmail.com>
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Marek: - various small rebase fixes and clean ups