[alsa] Fix port listing

[PolyMeilex]

Searching for either WRITE or SUB_WRITE capabilities causes filling of the ports list with a bunch of ports that are impossible to connect to and always return an error if you try to. I believe that the correct way is to search for both.

Alsa utils do the same: Search for readable: https://github.com/alsa-project/alsa-utils/blob/a566f8a0ed6d7ca5fd6ae2d224f3f28654a2f3be/seq/aplaymidi/arecordmidi.c#L685-L689 Search for writable: https://github.com/alsa-project/alsa-utils/blob/a566f8a0ed6d7ca5fd6ae2d224f3f28654a2f3be/seq/aplaymidi/aplaymidi.c#L832-L836