This adds DTX detection in PUCCH 2 receiver. This is detected by MAC
already which will drop PUCCH 2 indications that are detected as DTX.
For the moment this uses the same pucch0_dtx_threshold value indicated
in L1 section of the configuration file. The feature firstly reduces
unnecessary logging on stdout and the use of invalid CSI measurements in
the MAC scheduler.
Closes: #547
Robert Schmidt
dd7c3f80e8