Bluetooth: hidp: Don't release device ref if never held

When an hidp connection is added for a boot protocol input
device, don't release a device reference that was never
acquired. The device reference is acquired when the session
is linked to the session list (which hasn't happened yet when
hidp_setup_input is called).

Signed-off-by: Peter Hurley <peter@hurleysoftware.com>
Signed-off-by: Gustavo F. Padovan <padovan@profusion.mobi>