bus: mhi: host: pci_generic: Flush recovery worker during freeze

It is possible that the recovery work might be running while the freeze
gets executed (during hibernation etc.,). Currently, we don't powerdown
the stack if it is not up but if the recovery work completes after freeze,
then the device will be up afterwards. This will not be a sane situation.

So let's flush the recovery worker before trying to powerdown the device.

Cc: stable@vger.kernel.org
Fixes: 5f0c2ee1

 ("bus: mhi: pci-generic: Fix hibernation")
Reported-by: Bhaumik Vasav Bhatt <quic_bbhatt@quicinc.com>
Reviewed-by: Bhaumik Vasav Bhatt <quic_bbhatt@quicinc.com>
Link: https://lore.kernel.org/r/20220408150039.17297-1-manivannan.sadhasivam@linaro.org
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>