Changes

transceiver: use log level cache

This uses the newly added log level caching in libosmocore, which
prevents lock contention during the massive amount of usually disabled
but concurrent (threads) log statements.

Depends: libosmocore.git I539872fc9e3c50b407e6bc388f1e091fa2c826c3
Change-Id: Ic9f0e81c89827f2696ce046a3396f041703d6ae5