nvcodec: Mark class data as may-be-leaked to quiet the leaks tracer
The class data with the caps in it will be leaked if the element is registered but never instantiated. There is no way around this. Mark the caps as such so that the leaks tracer does not warn about it.
This is the same as pad template caps getting leaked, which are also marked as may-be-leaked. These objects are initialized exactly once, and are 'global' data.