fix umtrx-specific compilation warnings
backport time_spec improvements from upstream
Workaround for #3

This changeset prevents libusrp from trying to access the `gpsdo` parameter (which is unused with UmTRX). This allows tools using libusrp from starting even if the gpsdo parameter was set incorrectly on the board.
Merge pull request #4 from shimaore/patch-1

Don't use gpsdo in the UmTRX control class.
Merge pull request #2 from zabbal/fairwaves/umtrx

Fix umtrx-specific compilation warnings and backport time_spec api improvements to allow OpenLTE compilation.
Host: By default set LMS Icp to 0.2mA.

This gives much better results for the GMSK modulation.