ARM: dts: am335x: Set wakeup-source for UART0

ARM: dts: am335x: Set wakeup-source for UART0

On am335x evm[1], UART0(UART1-HW) has a wakeup capability.
Set wakeup-source, which will be used in the omap serial driver to enable
the device wakeup capability.

[1] https://www.ti.com/tool/TMDXEVM3358
[2] AM335x TRM - https://www.ti.com/lit/ug/spruh73q/spruh73q.pdf

Signed-off-by: Sukrut Bellary <sbellary@baylibre.com>
Tested-by: Judith Mendez <jm@ti.com>
Link: https://lore.kernel.org/r/20250318230042.3138542-4-sbellary@baylibre.com
Signed-off-by: Kevin Hilman <khilman@baylibre.com>