soc-qcom-sdm845: set MAC address on boot (MR 3360)

SDM845 devices running mainline lack a valid MAC address, and
fallback to a random one on each boot. This makes DHCP IPs vary
on each boot and breaks Bluetooth BNEP mode since the kernel enforces
that a valid MAC address is used when Bluetooth BNEP mode is activated.

Add a udev rule to trigger a script when the WLAN or Bluetooth interface
appear to set the MAC address by reading it from the persist partition
for the WLAN MAC address and increment it for generating a Bluetooth MAC
address. This approach seems to be common on some downstream devices
such as the Oneplus 6.

[ci:skip-build]: already built successfully in CI

device/community/soc-qcom-sdm845/APKBUILD

@@ -2,7 +2,7 @@
 pkgname=soc-qcom-sdm845
 pkgdesc="Common package for Qualcomm SDM845 devices"
 pkgver=8
-pkgrel=1
+pkgrel=2
 url="https://postmarketos.org"
 license="BSD-3-Clause"
 arch="aarch64"
@@ -11,12 +11,13 @@ depends="
 	mesa-dri-gallium
 	swclock-offset
 	msm-modem-uim-selection
+	bootmac
 "
 replaces="upower"
 subpackages="
 	$pkgname-nonfree-firmware:nonfree_firmware
-	$pkgname-ucm
 	$pkgname-qbootctl
+	$pkgname-ucm
 "
 
 _ucm_commit="621c71fd5f5742c60d38766ebb2d1bd3b863a2a4"