board: phytec: phytec_som_detection: Add support for phyFLEX

board: phytec: phytec_som_detection: Add support for phyFLEX

phyFLEX are SoMs based on the FPSC standard.

Add additional "SOM types" for the phyFLEX modules base on the
FPSC Gamma specification. These modules come in four different
variants; prototypes (PT), standard product (SP), KSP (KP) and
KSM (KM).

Signed-off-by: Daniel Schultz <d.schultz@phytec.de>
Reviewed-by: Teresa Remmet <t.remmet@phytec.de>
Tested-by: Dominik Haller <d.haller@phytec.de>