alsa-ucm: Make sure UCM uses DisableSequence
UCM only uses DisableSequence in "_disdev" if it was previously enabled by "_enadev". This can be easily reproduced by using alsaucm command.
For example, when both Headphone and Speaker are present before PulseAudio starts, Speaker will be disabled directly without getting enabled, and DisableSequence will be skipped.
So use "_enadev" before "_disdev" to make sure UCM uses DisableSequence. We don't need to worry about double enable because UCM already handles the case.
While at it, remove unnecessary comparison against zero.