media: v4l2-ctrls: Don't validate BITMASK twice

There is no need to repeat what check_range() does for us, i.e. BITMASK
validation in v4l2_ctrl_new().

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