wil6210: Initialize reply struct of the WMI commands

WMI command reply saved in uninitialized struct.
In order to avoid accessing unset values from FW initialize
the reply struct.

Signed-off-by: Alexei Avshalom Lazar <ailizaro@codeaurora.org>
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>