pine64-pinephone: align more closely to ALSA UCM specification

Some of the recommendations have changed upstream and a few devices should be called differently now. The following changes are made:

• Headphone -> Headphones (https://github.com/alsa-project/alsa-lib/blob/29041c522071172af2c6bf086b3a0c19510a6660/include/use-case.h#L136)
• DigitalMic -> Mic (https://github.com/alsa-project/alsa-lib/commit/1ad660ddeecb2a364f1ca62aa60f256f7029cfdc)
• HeadsetMic -> Headset (https://github.com/alsa-project/alsa-lib/blob/29041c522071172af2c6bf086b3a0c19510a6660/include/use-case.h#L137)
• Add .conf suffix for verb configurations
• Set Playback/CaptureChannels as integer, not as string
• Remove empty Enable/DisableSequence sections (https://github.com/alsa-project/alsa-ucm-conf/commit/d6a150d34f6e3a327215ad3452cfcfe164671717)

I'm making these changes to avoid future compatibility issues if applications start depending on these names.

AFAIK the only application that depends on particular names at the moment is plasma-dialer for voice calls (@bshah is working on a fix). Once this is sorted out the changes in this MR should not make any functional difference. Let's keep this WIP: until then.

NOTE: I don't have a PinePhone so someone else will need to test these changes.

Cc: @MartijnBraam @bshah