media: staging: atomisp: Remove dead code for MID (#4)

Since we switched to upstream IOSF MBI API the custom code
become not in use anymore.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@s-opensource.com>