serial: 8250: 8250_omap: Add DMA support for UARTs on K3 SoCs

UART on K3 SoCs has configurable RX timeout behavior (controlled via
EFR2) and better DMA integration. This allows to transfer as larger
amount data per DMA transfer compared to older SoCs.  Add support for
the same.

Signed-off-by: Vignesh Raghavendra <vigneshr@ti.com>
Link: https://lore.kernel.org/r/20200319110344.21348-7-vigneshr@ti.com


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