media: atomisp: Turn asd->streaming state tracker into a bool

The ATOMISP_DEVICE_STREAMING_STOPPING pipe state comes from when we still
had continuous mode. This would be set when streaming from both capture +
preview devnodes when 1 of the 2 streams has been stopped and the driver
was waiting for the other stream to get stopped too.

With continuous mode gone the stopping state is no longer necessary and
asd->streaming can be changed to a bool.

Note that atomisp_assert_recovery_work() would still temporarily
set streaming to stopping, but it does so with the isp->mutex held and
changes streaming to either enabled or disabled before releasing
the mutex, so none of the consumers which care about the difference
ever see the stopping state.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>