soc: renesas: identify RZ/A2

Add support for identifying the RZ/A2M (R7S9210) SoC.
Also add support for reading the BSID register which is a different format
than the PRR.

Signed-off-by: Chris Brandt <chris.brandt@renesas.com>
Reviewed-by: Geert Uytterhoeven <geert+renesas@glider.be>
Signed-off-by: Simon Horman <horms+renesas@verge.net.au>