console: Keep ->start() and ->stop() balanced

There is no need to call ->start() for already started device. All the same,
there is no need to call ->stop() for devices still in use.

For now enforce this only for IOMUX case.

Cc: Simon Glass <sjg@chromium.org>
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
1 file changed