misc: fastrpc: Safekeep mmaps on interrupted invoke

If the userspace daemon is killed in the middle of an invoke (e.g.
audiopd listerner invoke), we need to skip the unmapping on device
release, otherwise the DSP will crash. So lets safekeep all the maps
only if there is in invoke interrupted, by attaching them to the channel
context (which is resident until RPMSG driver is removed), and free them
on RPMSG driver remove.

Signed-off-by: Abel Vesa <abel.vesa@linaro.org>
Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Link: https://lore.kernel.org/r/20221125071405.148786-9-srinivas.kandagatla@linaro.org


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>