Reduce BLE connection logspam

Currenlty I observe lots of error logs when establishing BLE
connections:
bt_btu_hcif: packages/modules/Bluetooth/system/stack/btu/btu_hcif.cc:202 btu_hcif_log_event_metrics: Unexpectedly received event_code:0x3e that should not be handled here
This patch gets rid of those error logs

Test: compile, manual test
Change-Id: Icad82fcb0dfa24562a47e7e5593c6b333c0a48a6