drivers: qcom: qmi: Fix the race condition during QMI handle release

When the QMI client handle is released, the release operation waits only
for the threads whose request has been successfully transmitted and are
waiting for the responses. The release operation does not wait for the
threads whose requests are waiting for the flow control acknowledgement
from the remote side. This causes the QMI client handle to be freed
pre-maturely.

Wait for all the threads in an uninterruptible manner to exit before
freeing the QMI handle.

CRs-Fixed: 758124
Change-Id: I5bd0410dbed7d703b1c8652a916a130a5a4e5abe
Signed-off-by: Karthikeyan Ramasubramanian <kramasub@codeaurora.org>