dt-bindings: input: touchscreen: tsc2007: Document 'wakeup-source'

The 'wakeup-source' property is used by many devicetree files and is
also supported by the tsc2007_core driver.

Document it to avoid the following dt-schema warning:

'wakeup-source' does not match any of the regexes: '^pinctrl-[0-9]+$'

Signed-off-by: Fabio Estevam <[e-mail]>
Acked-by: Conor Dooley <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Dmitry Torokhov <[e-mail]>

Documentation/devicetree/bindings/input/touchscreen/ti,tsc2007.yaml

···
 
   pendown-gpio: true
 
+  wakeup-source: true
+
   ti,max-rt:
     $ref: /schemas/types.yaml#/definitions/uint32
     description: maximum pressure.