dt-bindings: gpio: pca95xx: add entry for pcal6408

The NXP PCAL6408 is the 8-bit version of PCAL6416.
Signed-off-by: NNate Drude <nate.d@variscite.com>
Signed-off-by: NBartosz Golaszewski <brgl@bgdev.pl>

Documentation/devicetree/bindings/gpio/gpio-pca95xx.yaml

@@ -47,6 +47,7 @@ properties:
       - nxp,pca9574
       - nxp,pca9575
       - nxp,pca9698
+      - nxp,pcal6408
       - nxp,pcal6416
       - nxp,pcal6524
       - nxp,pcal9535