serial: atmel: Use platform_get_irq() to get the interrupt

Accessing platform device resources directly has long been deprecated for
DT as IRQ resources may not be available at device creation time. Drivers
continuing to use static IRQ resources is blocking removing the static setup
from the DT core code.

Signed-off-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20211215224832.1985402-1-robh@kernel.org


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