How it works:
1. Current Meter Source on FC is set to MSP/OSD Slave by user.
2. On reboot FC sends MSP_ANALOG to OSD Slave.
3. OSD Slave listens for incoming MSP as usual.
4. OSD responds to MSP as usual.
6. The FC recevies the data from the OSD Slave and updates the MSP
Current Meter.
update the MSP configuration of current and voltage sensors to use IDs.
revert the i2s_bst changes, since TBS won't be updating their firmware
there is no point adding new features to it, we just need to keep it
compatible
