This split allows us to distingush between the SOC types.
The SOC symbols will be used in following patches.
SOC_SAMA5D2 is essential unused for now,, and only added
to prepare for future use

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
Tested-by: Ladislav Michl <ladis@linux-mips.org>
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>