arm: SC594-SOM-EZKIT initial support

arm: SC594-SOM-EZKIT initial support

Adds support for Analog Devices' SC594-SOM-EZKIT board. Includes:
- SoC specific configs in mach-sc5xx/Kconfig
- Memory Map for SPL
- SPL config options in common/spl/Kconfig
- Necessary board-specific init functions
- Board-specific Kconfig and environment in board/adi/
- Memory configuration

Co-developed-by: Greg Malysa <greg.malysa@timesys.com>
Signed-off-by: Greg Malysa <greg.malysa@timesys.com>
Co-developed-by: Trevor Woerner <twoerner@gmail.com>
Signed-off-by: Trevor Woerner <twoerner@gmail.com>
Co-developed-by: Nathan Barrett-Morrison <nathan.morrison@timesys.com>
Signed-off-by: Nathan Barrett-Morrison <nathan.morrison@timesys.com>
Co-developed-by: Ian Roberts <ian.roberts@timesys.com>
Signed-off-by: Ian Roberts <ian.roberts@timesys.com>
Signed-off-by: Oliver Gaskell <Oliver.Gaskell@analog.com>