calib: The call to fscanf can fail and we should check the return value
calib: The call to fscanf can fail and we should check the return value

Coverity wants us to check that fscanf has scanned the amount of
variables we want to have. Initialize the scan result to 0/0.0f
and warn if the scan has failed.

Fixes: Coverity CID 1040774, CID 1040773

geosphere/osmo-bts,geosphere/osmo-bts,osmocom/osmo-bts,telenoobie/osmo-bts,geosphere/osmo-bts,telenoobie/osmo-bts,geosphere/osmo-bts,telenoobie/osmo-bts,osmocom/osmo-bts,telenoobie/osmo-bts,osmocom/osmo-bts