tty: serial: atmel: make it selectable for ARCH_LAN969X

LAN969x uses the Atmel serial, so make it selectable for ARCH_LAN969X.

Signed-off-by: Robert Marko <robert.marko@sartura.hr>
Acked-by: Nicolas Ferre <nicolas.ferre@microchip.com>
Link: https://lore.kernel.org/r/20250108131045.40642-3-robert.marko@sartura.hr


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