wil6210: publish/receive WMI events/commands through nl

For general debug purposes added functionality for sending WMI
events and receiving WMI commands to/from user-space through vendor
commands.

Change-Id: I889d30bf1f060f75d7ae933735d1d959e53e513e
Signed-off-by: Alexei Avshalom Lazar <ailizaro@codeaurora.org>