sysmobts: Cache the eeprom_Cfg_t for reading tx/rx calib data
sysmobts: Cache the eeprom_Cfg_t for reading tx/rx calib data

The current code has 26 fseek/fread. Only the minority really results
in a call to read. Nevertheless the time for reading during the bootstrap
can take up to 7.82 seconds. Caching the header (which is already done
by fopen/fread) will result in one call to fseek/fread and only
consumes 0.784 seconds.

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