soc-qcom-sdm845: set MAC address on boot

• Add qmac as a script to retrieve the MAC address on boot from /mnt/persist to set it for WLAN and Bluetooth interfaces on SDM845. May work for other devices, but that's untested.
• Let the SHIFT 6mq device package depend on soc-qcom-sdm845-qmac to enable this functionality. Other SDM845 may work fine with this as well, but I leave that to other device maintainers to test and enable this functionality for their devices as I cannot verify this.
• While at it, let the SHIFT 6mq device package also depend on soc-qcom-sdm845-upower to shut it down when the battery is low, enables the functionality introduced in !3287 (merged)
• Fixes the following annoying issues:
  • IP from DHCP over WiFi changes on each boot
  • Bluetooth BNEP failed to work since the MAC address was not a valid one

CC: @sdm845-mainline