net/mgmt: Add a network interface based synchronous event listener

In case of callback based event listener, it is easy for the callback to
filter on the given interface. But in case of the synchronous call it's
not: it would need, after a failed comparison on the interface pointer
to loop by itself on the net_mgmt_event_wait() which is a little bit
heavy (reinstalling the event listener, with the semaphore and all) and
a bit of a burden for the caller itself.

Instead, net_mgmt provides a dedicated call
net_mgmt_event_wait_on_iface() which does it the right way, so the
callback and the related semaphore are destroyed if only the iface
matches the one given as parameter (besides the timeout obviously).

Change-Id: Iab05c3249586f4f4d0447eea42fdac72b8428f2e
Signed-off-by: Tomasz Bursztyka <tomasz.bursztyka@linux.intel.com>