arm: dts: Support SC573-EZKIT

arm: dts: Support SC573-EZKIT

Adds minimal device tree for Analog Devices' SC573-EZKIT board and
common files for the SC57x/SC5xx family.

This also adds all sc5* devicetrees to ARM SC5XX in MAINTAINERS, and
adds the ADSP Linux mailing list as the list for ARM SC5XX.

Co-developed-by: Greg Malysa <greg.malysa@timesys.com>
Signed-off-by: Greg Malysa <greg.malysa@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: Oliver Gaskell <Oliver.Gaskell@analog.com>