bladeRF: have it functional with libbladerf 2.0

Not much has been changed in the driver (that used libbladerf 1.0).
Some bugs have been fixed. Documentation has been added. A configuration
file has been added too, put in the directory ./configuration/bladeRF.

To use a bladeRF device, see documentation in targets/ARCH/BLADERF/README.

Only the BladeRF x40 has been tested.

Performance is not too bad at 5MHz, a bit worse at 10MHz and on the test
machine I used I face realtime problems at 20MHz when I push downlink
throughput.

So, there is still some work to do to have a good support of bladeRF.
13 jobs for <span class="ref-name">bladerf-support-fix-2018-w45</span> in 0 seconds (queued for 14 minutes and 48 seconds)
Status Job ID Name Coverage
  External
passed Analysis with cppcheck

00:05:25

passed Build UE-ethernet

00:03:14

passed Build basic-sim

00:00:03

passed Build eNb-USRP

00:00:22

passed Build eNb-USRP-CentOS

00:06:20

passed Build eNb-ethernet

00:00:58

passed Build phy-sim

00:04:48

passed Test basic-sim

00:10:22

passed Test phy-sim

00:10:31

passed Test-FDD-Band7

00:40:59

passed Test-IF4p5-FDD-Band7

00:53:46

passed Test-IF4p5-TDD-Band40

00:47:03

passed Test-TDD-Band40

00:15:20