main/linux-postmarketos-qcom-msm8916: upgrade to 5.7.1

We are in the midst of the Linux 5.8 merge window so there is no new -rc version to rebase on. -rc1 next week is also not the perfect choice for a release (first rc is usually still a bit unstable). On the other hand the changes that landed the last few days are quite nice and ready to go, so I decided to rebase on a stable kernel release (5.7.1). Not sure if I'm ever going to do this again :)

Changes:

• Update to Linux 5.7.1
• bq-paella: Add sound and modem (contributed by @lazzardo, including a new driver for the speaker)
• Enable some new kernel options for DB410c (contributed by @Minecrell)

For soc-qcom-msm8916:

• Add ALSA UCM configuration for bq-paella (there is an external amplifier connected to the right channel of the headphones output)

Cc: @Mis012 @TravMurav @jja2000 @srxl @rvlander @lazzardo @minlexx @jugendhacker @LorenDB