dt-bindings: serial: brcm,bcm2835-aux-uart: convert to dtschema

dt-bindings: serial: brcm,bcm2835-aux-uart: convert to dtschema

Convert the Broadcom BCM2835 Auxiliary UART to newer DT schema.
Created DT schema based on the .txt file which had
`compatible`, `reg` `clocks` and `interrupts` as the
required properties. This binding is used by Broadcom BCM2835
SOC used in some Raspberry PI boards.
Changes from original file:
Implemented complete example which the original txt binding lacked.

Acked-by: Florian Fainelli <florian.fainelli@broadcom.com>
Reviewed-by: Conor Dooley <conor.dooley@microchip.com>
Signed-off-by: Pratik Farkase <pratik.farkase@wsisweden.com>
Link: https://lore.kernel.org/r/20240425162554.13576-1-pratik.farkase@wsisweden.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>