dt-bindings: serial: Convert microchip,pic32mzda-uart to DT schema

Convert the Microchip PIC32 UART binding to DT schema. The binding was
unclear there are 3 interrupts. The functions were determined from the
driver. The 'cts-gpios' property is covered by serial.yaml schema.

Signed-off-by: "Rob Herring (Arm)" <robh@kernel.org>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Link: https://lore.kernel.org/r/20250507154937.1603190-1-robh@kernel.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>