dt-bindings: input: google,goldfish-events-keypad: Convert to DT schema

dt-bindings: input: google,goldfish-events-keypad: Convert to DT schema

Convert the Android Goldfish Events Keypad binding to DT schema format.
Move the file to the input directory to match the subsystem.
Update the example node name to 'keypad' to comply with generic node
naming standards.

Signed-off-by: Kuan-Wei Chiu <visitorckw@gmail.com>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@oss.qualcomm.com>
Link: https://patch.msgid.link/20260113092602.3197681-4-visitorckw@gmail.com
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>