dt-bindings: riscv: correct starfive visionfive 2 compatibles

Using "va" and "vb" doesn't match what's written on the board, or the
communications from StarFive.
Switching to using the silkscreened version number will ease confusion &
the risk of another spin of the board containing a "conflicting" version
identifier.
As the binding has not made it into mainline yet, take the opportunity
to "correct" things.

Suggested-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>
Link: https://lore.kernel.org/linux-riscv/Y+4AxDSDLyL1WAqh@wendy/


Fixes: 97b7ed07 ("dt-bindings: riscv: Add StarFive JH7110 SoC and VisionFive 2 board")
Signed-off-by: Conor Dooley <conor.dooley@microchip.com>
Acked-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230216131511.3327943-1-conor.dooley@microchip.com


Signed-off-by: Arnd Bergmann <arnd@arndb.de>