Unpair HID device cleanup

When unparing HID devices, the attr_mask was not cleared.
By not clearing this data, some HID device will never be able
to connect again. (E.g. the Apple Magic Mouse)

Bug: 15566403
Change-Id: Ic80909dcecdf48d967c1a936b31554653761fa42
Signed-off-by: Casper Bonde <c.bonde@samsung.com>