LMSDevice: make use of dev-args in osmo-trx.cfg

Allow selecting a specific LimeSDR device by setting dev-args in the
config file. Split up the given dev-args address by comma and select
the device where all substrings can be found.

I could not test this with real hardware, but I have added a test case
to make sure this works as expected.

Related: OS#3654
Change-Id: Ib9aaa066a01bf9de3f78234d7ada884d6f28c852
5 files changed