WIFIHAL: Support to send nl requests through wifihal

Added support in wifihal to send nl messages on behalf
of its clients. Since netadmin capabilities are
given to wifihal, it is used as bridge to send nl
messages to kernel
Added support for clients to register for nl events.

CRs-Fixed: 2424237
Bug: 131618408
Bug: 28340421
Test: Regression test

Change-Id: If8b62733e1d298804e0be98918eb875fc52a4ad1
Signed-off-by: Srinivas Girigowda <quic_sgirigow@quicinc.com>