device-pine64-pinephone: reduce diff between upstream alsa ucm conf and ours (MR 5462)

Upstream ALSA UCM conf still does not work exactly for us, but parts of it do.
This commit incorporates those parts to reduce the diff between the two.

One of the changes is to move /usr/share/alsa/ucm2/PinePhone/* to
.../ucm2/Allwinner/A64/PinePhone/* to match upstream, and to
stop creating the symlink .../ucm2/conf.d/simple-card/PinePhone.conf
since upstream already provides it. However this means that just upgrading
device-pine64-pinephone will remove the symlink and not replace the symlink
from upstream package. Users will need to run
`apk fix --reinstall alsa-ucm-conf` to recreate it, and will not have sound
until they do.

Ref: #2115