package/iperf3: bump to 3.7

package/iperf3: bump to 3.7

- Dropped musl and profiling patches as they were incorporated upstream.
- Profiling is set as explicitly disabled as it can now be configured.
- License file hash is changed due to an update in the copyright year:
  -"iperf, Copyright (c) 2014-2018, The Regents of the University of California,
  +"iperf, Copyright (c) 2014-2019, The Regents of the University of California,

Signed-off-by: Matthew Weber <matthew.weber@rockwellcollins.com>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@bootlin.com>