For half duplex channels we dont have separate interrupts for Tx and Rx
instead we have single interrupt Rt (where the signal for Rx and Tx is
muxed). To handle such a case install a handler in case we have a dma_rt
interrupt specified in the DT for the PIO mode.

Note, for backward compatibility we check if the Rx and Tx interrupts
are present first instead of checking Rt interrupt.
Signed-off-by: Lad Prabhakar <prabhakar.mahadev-lad.rj@bp.renesas.com>
Reviewed-by: Biju Das <biju.das.jz@bp.renesas.com>
Link: https://lore.kernel.org/r/20230217185225.43310-3-prabhakar.mahadev-lad.rj@bp.renesas.comSigned-off-by: Mark Brown <broonie@kernel.org>