The "+BIND: <a>,<state>" reply to AT+BIND? should be sent for every
supported indicator.
"AT+BIEV= <assigned number>,<value>" should only be provided for
enabled indicators. The AG shall respond with an ERROR response code
if it receives updates for disabled or unknown HF indicators or values
that are out of bounds.
This allows to pass PTs tests:
- HFP/AG/HFI/BV-02-C
AG receives an updated HF Indicator value
- HFP/AG/HFI/BI-03-C
AG receives invalid updated HF Indicator values