While the CDB Assist and QcomLT Debugboard is measuring voltage and
current on the DC jack directly in the backend, other backends and
further measurements can be performed using custom tooling.
Introduce support for invoking an external "status-cmd" to produce such
status updates.
The status command should on its stdout produce json-formatted status
updates following the same format as the cdba-server:
{"ts":%d.%03d, "name": {["mv"|"ma"]: %u}(, "name2": {["mv"|"ma"]: %u})*}
with the ts aquired using clock_gettime(CLOCK_MONOTONIC) and provided in
seconds and milliseconds since the first measurement.
Signed-off-by: Bjorn Andersson <quic_bjorande@quicinc.com>
