Clearing a channel context can happen twice if the client driver
unprepares and reset the channels from the remove() callback from
a controller requested MHI power down sequence. If there are
multiple attempts at calling the mhi_free_coherent() API, we see
kernel warnings such as "trying to free invalid coherent area".
Example for one such client is the QRTR MHI driver. Avoid these
warnings by skipping mhi_deinit_chan_ctxt() API call and prevent
extra work from MHI as the channels are already disabled.
Signed-off-by: Bhaumik Bhatt <bbhatt@xxxxxxxxxxxxxx>