arm64: dts: ti: k3-am625-beagleplay: Use UART name in pinmux name

The main_uart0 may not always be the console, but it will always be
the UART0 in MAIN domain. Name the pinmux node to match. This makes
it consistent with all other TI SoC based boards.

Signed-off-by: Andrew Davis <afd@ti.com>
Link: https://lore.kernel.org/r/20231127193602.151499-1-afd@ti.com


Signed-off-by: Nishanth Menon <nm@ti.com>