dt-bindings: clocks: atmel,at91rm9200-pmc: convert to yaml

Convert Atmel PMC documentation to yaml. Along with it clock names
were adapted according to the current available device trees as
different controller versions accept different clock (some of them
have 3 clocks as input, some has 2 clocks as inputs and some with 2
input clocks uses different clock names).

Signed-off-by: Claudiu Beznea <claudiu.beznea@microchip.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Link: https://lore.kernel.org/r/20230517094119.2894220-3-claudiu.beznea@microchip.com