Add amixer --view, to filter playback, capture or all

alsa-project/alsa-utils issue #67 was edited from jidanni:

alsamixer has ``` -V, --view <mode> Select the starting view mode, either playback, capture or all. ```

Perhaps amixer could also have something similar, e.g., so that ``` $ amixer --view capture ``` would only dump the capture related settings. Currently one could say that ``` $ amixer --view all ``` is the default.

Issue URL : https://github.com/alsa-project/alsa-utils/issues/67 Repository URL: https://github.com/alsa-project/alsa-utils