amixer: Expand on channel docs in man page

alsa-project/alsa-utils pull request #78 was opened from mcampbellizo:

Add missing channel params to the amixer man page. Also call out that the channel param must come before the value to take effect.

signed-off-by: Matthew Campbell mcampbell@izotope.com

Request URL : https://github.com/alsa-project/alsa-utils/pull/78 Patch URL : https://github.com/alsa-project/alsa-utils/pull/78.patch Repository URL: https://github.com/alsa-project/alsa-utils