osmo-bts-trx: set l1c logging level to notice

We have sporadic osmo-bts-trx shutdowns with "No clock from osmo-trx" error
messages. Around it are L1C logs on level 'notice', so let's log those as well.

Related: OS#2325
Change-Id: Ic306d2dd8670550d84e9c446098bccaba147e13b
1 file changed