arch: arm: Add Analog Devices SC5xx machine type

Add support for the SC5xx machine type from Analog Devices. This
includes support for the SC57x, SC58x, SC59x, and SC59x-64 SoCs, which
have many common features such as common ADI IP blocks, and SHARC DSP
cores. This commit introduces core functionality required for all boards
using an SC5xx SoC, such as:

- SPL configuration
- Required CPU hooks such as reset
- Boot ROM interaction to load the stage 2 bootloader in the reference
  configuration. Other options are possible but not officially supported
  at this time
- SoC-common configuration expected to be reused by all boards
- Early initialization for system clocks and DDR controller

Co-developed-by: Greg Malysa <greg.malysa@timesys.com>
Signed-off-by: Greg Malysa <greg.malysa@timesys.com>
Co-developed-by: Ian Roberts <ian.roberts@timesys.com>
Signed-off-by: Ian Roberts <ian.roberts@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: Nathan Barrett-Morrison <nathan.morrison@timesys.com>