PP 1.2 and PPP configs were lacking this parameter. Although it's not a
problem as `eg25-manager` will then use a default value, adding them
won't harm and make them more consistent with other config files.
As the modem is connected to a dedicated audio codec, we can select any
sample rate. Let's go for 16K as it should improve call audio quality.
Note: the bitclock's frequency is left untouched due to a bug in the
EG25 kernel, so we can't take advantage of the recommended higher
frequency.
The PinePhone Pro uses the same EG25 modem as the OG PinePhone, but with
a different SoC. It also uses an ALC5616 audio codec directly hooked up
to the modem (which is I2S master in this case).
The config is therefore almost identical to the PinePhone rev1.2 except
for the gpios, UART port used and `AT+QDAI` config (to account for the
different audio setup).
