BACKPORT: Input: goldfish_events - add devicetree bindings

Add device tree bindings to the Goldfish virtual platform event driver.

Signed-off-by: Greg Hackmann <ghackmann@google.com>
Signed-off-by: Jin Qian <jinqian@android.com>
Signed-off-by: Alan <alan@linux.intel.com>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
(cherry picked from commit 8c5dc5a1ada2b79259e55a4bd150135d23529c6a)

Change-Id: I677d8e0d92294f53f7cc5a79300b6462b65e8aad