serial: amba-pl011: Do not complain when DMA is absent

Many SoCs do not integrate DMA for the amba pl011 UART, causing
the following message on boot:

uart-pl011 80074000.serial: no DMA platform data

The UART still works in PIO, so better not to print such message that
may confuse people by causing them to think that there is something wrong
with the UART.

Change the message to debug level.

Signed-off-by: Fabio Estevam <festevam@denx.de>
Link: https://lore.kernel.org/r/20230928145842.466933-1-festevam@gmail.com


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