Third set of IIO fixes for the 3.12 cycle. Two little ones this time: 1) A missing clk_unprepare in adf4350. 2) A missing free of the active_scan_mask when iio_disable_all_buffers is called during an unexpected device removal. This leak was introduced by the fix a87c82e454f184a9473f8cdfd4d304205f585f65 iio: Stop sampling when the device is removed and hence is a regression fix.