main/linux-postmarketos-qcom-msm8916: upgrade to 5.6-rc2

• Update to Linux 5.6-rc2
• Major improvements for Motorola Moto G4 Play (motorola-harpia) (contributed by @srxl)
  • Display
  • Touchscreen
  • Accelerometer
  • Audio
  • Modem
  • Vibrator
• Fix headphones/headset detection for wileyfox-crackling
• Add mount-matrix for samsung-a3ulte/a5ulte to fix orientation detection with iio-sensor-proxy (with contribution from @Mis012)
• A lot of cleanup everywhere
• APKBUILD: Clean up makedepends (a lot of them are unneeded)

Cc: @TravMurav