dt-bindings: mfd: google,cros-ec: Add missing properties

Add common properties appearing in DTSes (controller-data,
wakeup-source) to partially fix dtbs_check warnings like:

  arch/arm/boot/dts/exynos5250-snow.dt.yaml: embedded-controller@1e:
    'keyboard-controller', 'wakeup-source' do not match any of the regexes: 'pinctrl-[0-9]+'

  arch/arm/boot/dts/exynos5800-peach-pi.dt.yaml: cros-ec@0:
    'controller-data', 'i2c-tunnel', 'keyboard-controller' do not match any of the regexes: 'pinctrl-[0-9]+'
Signed-off-by: Krzysztof Kozlowski <krzk@kernel.org>
Link: https://lore.kernel.org/r/20200903191407.12686-1-krzk@kernel.orgSigned-off-by: Rob Herring <robh@kernel.org>

Documentation/devicetree/bindings/mfd/google,cros-ec.yaml

@@ -30,6 +30,11 @@ properties:
           For implementations of the EC is connected through RPMSG.
         const: google,cros-ec-rpmsg
 
+  controller-data:
+    description:
+      SPI controller data, see bindings/spi/spi-samsung.txt
+    type: object
+
   google,cros-ec-spi-pre-delay:
     description:
       This property specifies the delay in usecs between the
@@ -63,6 +68,9 @@ properties:
   interrupts:
     maxItems: 1
 
+  wakeup-source:
+    description: Button can wake-up the system.
+
 required:
   - compatible