samsung-crownlte: add Bluetooth support

Packaged firmware for Bluetooth, adjusted kernel config to support hciattach, wrote an OpenRC service for hciattach (just to avoid using killall hciattach) and a udev rule that starts and stops the service whenever user unblocks or blocks the BT adapter in rfkill.

This was done to fix two problems I've encountered with hciattach:

• it requires a fresh start after a block-unblock cycle, otherwise HCI adapter returns "busy" errors
• it relies on adapter being unblocked when it starts (if it isn't, hciattach service will hang and timeout)

To avoid this complexity I wanted to use btattach, which (IIRC) doesn't care about rfkill status and doesn't require installing bluez-deprecated. However, it drops UART baud rate to 115200 bps after firmware upload, which reduces audio quality by a large margin. https://wiki.postmarketos.org/index.php?title=Samsung_Galaxy_Note_9_(Exynos)_(samsung-crownlte)&oldid=28482#Bluetooth

Tested on xfce4, hopefully this change is DE independent.