HID: magicmouse: Do not crash on missing msc->input

HID: magicmouse: Do not crash on missing msc->input

Fake USB devices can send their own report descriptors for which the
input_mapping() hook does not get called.  In this case, msc->input stays NULL,
leading to a crash at a later time.

Detect this condition in the input_configured() hook and reject the device.

This is not supposed to happen with actual magic mouse devices, but can be
provoked by imposing as a magic mouse USB device.

Cc: stable@vger.kernel.org
Signed-off-by: Günther Noack <gnoack@google.com>
Signed-off-by: Jiri Kosina <jkosina@suse.com>