package/iperf: update sha256 hash

Commit ca39eb212e32ca209cb3d6011847f9c94641fa73 forgot to update sha256
hash

Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com>
Reviewed-by: Peter Seiderer <ps.report@gmx.net>
Signed-off-by: Yann E. MORIN <yann.morin.1998@free.fr>

package/iperf/iperf.hash

@@ -2,5 +2,5 @@
 sha1  b9d0868a6cdd970c1835d3d1a264dd54907f2c5c  iperf-2.1.5.tar.gz
 
 # Locally computed:
-sha256  062b392e87b8e227aca74fef0a99b04fe0382d4518957041b508a56885b4d4f9  iperf-2.1.4.tar.gz
+sha256  56ec1312d24bd2c78790e67c96c0a991c82e71bc4c0b0d37171bd89c9fd6ef3e  iperf-2.1.5.tar.gz
 sha256  5f9f5c4feca3347c3b3c0ada8b16b4e6b698aac4e6f016a24adf61a5915336d1  COPYING