dma: Add driver for ADI SC5xx-family SoC MDMA functionality

dma: Add driver for ADI SC5xx-family SoC MDMA functionality

Add a rudimentary MDMA driver for the Analog Devices SC5xx SoCs,
primarily intended for use with and tested against the QSPI/OSPI
IP included in the SoC.

Co-developed-by: Ian Roberts <ian.roberts@timesys.com>
Signed-off-by: Ian Roberts <ian.roberts@timesys.com>
Co-developed-by: Nathan Barrett-Morrison <nathan.morrison@timesys.com>
Signed-off-by: Nathan Barrett-Morrison <nathan.morrison@timesys.com>
Signed-off-by: Vasileios Bimpikas <vasileios.bimpikas@analog.com>
Signed-off-by: Utsav Agarwal <utsav.agarwal@analog.com>
Signed-off-by: Arturs Artamonovs <arturs.artamonovs@analog.com>
Signed-off-by: Greg Malysa <malysagreg@gmail.com>
Signed-off-by: Oliver Gaskell <Oliver.Gaskell@analog.com>