CHROMIUM: WAR: Bluetooth: hci_qca: Send vendor specific

pre shut down command before turning off regulators.

For BT coex to have proper state, SOC needs VS pre shutdown command
while turning off the BT.
So for that in shutdown sequence first sending the pre shutdown
command and then turn off the regulators.

BUG=b:137305221
BUG=b:135951625
TEST=Validate behavior with Coex test scenarios for BT/Wifi

Change-Id: If686113fefb58e9972e342006570252f2007eb01
Signed-off-by: Harish Bandi <c-hbandi@codeaurora.org>
Signed-off-by: Mayank Chopra <mak.chopra@codeaurora.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/third_party/kernel/+/1702630


Reviewed-by: Yixiang Li <yixiang@google.com>
Reviewed-by: Julan Hsu <julanhsu@google.com>
Tested-by: Yixiang Li <yixiang@google.com>
Tested-by: Sivarama Krishna Eluri <eluris@google.com>
Legacy-Commit-Queue: Commit Bot <commit-bot@chromium.org>