iperf: Add version 2.0.4 (initial recipe)

* Imported from oe.dev commit id 0ff10ecb88de73074ae4857046643cef15dc4e97 and c10c33f86903c93611023197a7f812459c2dfe2d.
* Combined .inc and bb file from oe.dev and made a single bb file.
* Removed EXTRA_OECONF_append_epia = " --disable-threads" while importing as this should go in epia layer.

Signed-off-by: Noor Ahsan <noor_ahsan@mentor.com>