HID: magicmouse: fix input registration

When HIDRAW is not set, hid_hw_start() returns ENODEV as no subsystem has
claimed the magicmouse device, and probe routine bails out. Which is not what we want.

This happens because magicmouse driver is instantiating the connection to
Input subsystem itself, and since commit 28918c21

 ("HID: magicmouse: fix
oops after device removal") the HID core is not registering input device
itself.

Fix this by letting HID core register the input device (so that hid_hw_start()
succeeds, as the device is claimed by at least one subsystem) and de-register
it again later before proceeding with proper input setup.

Reported-by: Justin P. Mattock <justinmattock@gmail.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>