wil6210: missing reinit_completion in wmi_call

The code in wmi_call uses the wil->wmi_call completion
structure to wait for a reply.
In some scenarios, complete was called twice on the
completion structure. This happened mainly with a disconnect
event which can arrive both unsolicited and as a reply to
a disconnect request. In this case the completion structure
was left marked as "done" and the next wmi_call returned
immediately with a corrupted reply buffer. This caused
unexpected results including crashes.
Fix this by adding the missing call to reinit_completion.

CRs-Fixed: 1105246
Change-Id: I4de26881620dde4230d0a907bd0fd39bebe2bb3d
Signed-off-by: Hamad Kadmany <hkadmany@codeaurora.org>