ARM: dts: microchip: sam9x60: Add missing property atmel,usart-mode

ARM: dts: microchip: sam9x60: Add missing property atmel,usart-mode

[ Upstream commit 2f9d013a0c6f1b9109ada5acb28ee26eefc77c03 ]

Add the atmel,usart-mode property to the UART nodes. This ensures
compliance with the atmel,at91-usart.yaml schema and resolves the errors
below:
serial@200: $nodename:0: 'serial@200' does not match
'^spi(@.*|-([0-9]|[1-9][0-9]+))?$'
serial@200: atmel,use-dma-rx: False schema does not allow True
serial@200: atmel,use-dma-tx: False schema does not allow True
serial@200: atmel,fifo-size: False schema does not allow [[16]]

These errors indicate that the property
atmel,usart-mode = <AT91_USART_MODE_SERIAL> is missing for
UART nodes 0, 1, 2, 3, 4, 6, 7, 8, 9, 10, 11, and 12.

Fixes: 99c808335877 ("ARM: dts: at91: sam9x60: Add missing flexcom definitions")
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Signed-off-by: Andrei Simion <andrei.simion@microchip.com>
Link: https://lore.kernel.org/r/20240912093307.40488-1-andrei.simion@microchip.com
[claudiu.beznea: move the atmel,usart-mode close to vendor specific
 properties to cope with DTS coding style]
Signed-off-by: Claudiu Beznea <claudiu.beznea@tuxon.dev>
Signed-off-by: Sasha Levin <sashal@kernel.org>