Bluetooth broken on the PinePhone with firmware from linux-firmware

Bluetooth no longer works on pine64-pinephone after we switched from our own fw to the one shipped in linux-firmware package.

Original discussion: !5582 (comment 2113476321)

Confirmed on my phone too. Scanning does not find anything with the linux-firmware fw. Restoring the rtl8723cs_xx_*.bin from https://github.com/anarsoul/rtl8723bt-firmware/tree/master/rtl_bt and reloading the kmod makes scanning and pairing work.

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The linux-firmware files come from realtek.com, as per its commit message. The anarsoul ones might've come from pine64 given their original filenames.

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Options:

1. Bring back the firmware-pine64-rtl8723bt package and remove the dep on linux-firmware-rtl_bt instead.

2. Bring back the firmware-pine64-rtl8723bt package but change the filenames to have a _pine64 suffix, and patch the allwinner kernel to load them instead. ( https://github.com/torvalds/linux/blob/a430d95c5efa2b545d26a094eb5f624e36732af0/drivers/bluetooth/btrtl.c#L162-L163 -> https://github.com/torvalds/linux/blob/a430d95c5efa2b545d26a094eb5f624e36732af0/drivers/bluetooth/btrtl.c#L1189-L1212 )

3. Bring back the firmware-pine64-rtl8723bt package and mark it as replaces=linux-firmware-rtl_bt

4. ???

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cc @airtower-luna