Move the shelli-specific alsa config from MR 1741 into a subpackage that
only gets installed together with shelli.
With the config installed, programs using alsa instead of pulseaudio,
can't be controlled through the volume setting in Phosh anymore (and
probably other UIs too). Shelli doesn't use pulseaudio.
Change the path of the config file like in MR 1877, so it's easier to
override it if necessary.
While at it, improve the APKBUILD slightly by fixing the install_if of
the phosh subpkg (should depend on =$pkgver-r$pkgrel, see APKBUILD
reference), and fix long lines.
4b8f37e46e