dt-bindings: watchdog: imx7ulp-wdt: Add imx93 compatible string

The wdog on i.MX93 is modified from i.MX8ULP with some changes,
it uses one compatible string, so add i.MX93 support.

Signed-off-by: Peng Fan <[e-mail]>
Acked-by: Rob Herring <[e-mail]>
Reviewed-by: Guenter Roeck <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Guenter Roeck <[e-mail]>
Signed-off-by: Wim Van Sebroeck <[e-mail]>

Documentation/devicetree/bindings/watchdog/fsl-imx7ulp-wdt.yaml

···
       - items:
           - const: fsl,imx8ulp-wdt
           - const: fsl,imx7ulp-wdt
+      - const: fsl,imx93-wdt
 
   reg:
     maxItems: 1