dt-bindings: eeprom: at25: use "size" for FRAMs without device ID

Not all FRAM chips have a device ID and implement the corresponding read
command. Thus the memory size, which is contained in the device ID,
cannot be detected and has to be set manually as it is done for EEPROMs.

Link: https://lore.kernel.org/all/[e-mail]/
Signed-off-by: Markus Heidelberg <[e-mail]>
Reviewed-by: Rob Herring (Arm) <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Greg Kroah-Hartman <[e-mail]>

Documentation/devicetree/bindings/eeprom/at25.yaml

···
     $ref: /schemas/types.yaml#/definitions/uint32
     description:
       Total eeprom size in bytes.
+      Also used for FRAMs without device ID where the size cannot be detected.
 
   address-width:
     $ref: /schemas/types.yaml#/definitions/uint32
···
             compatible = "cypress,fm25", "atmel,at25";
             reg = <1>;
             spi-max-frequency = <40000000>;
+        };
+
+        fram@2 {
+            compatible = "cypress,fm25", "atmel,at25";
+            reg = <2>;
+            spi-max-frequency = <20000000>;
+            size = <2048>;
         };
     };