media: staging: atomisp: Remove duplicate declaration in header

There are 3 declarations that are present in atomisp_platform.h and
atomisp_gmin_platform.h. Remove duplications from the latter.

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>