videoconvert: New checks are too strict breaking padded allocation cases

Passing padded width/height is getting more and more common. This is achieve by giving padded width/height to the allocator, this was first used by the gstreamer-vaapi plugins. The side effect is that the VideoMeta represent the padded width/height while the caps represent the display width/height. As this is just padding, element using VideoMeta should have to be aware hence should not fail on such a difference.

The following discussion from !696 (merged) should be addressed:

• @ndufresne started a discussion:

  This check is too strict. In my case I got a in-frame that has display of 1920x1080, but has been allocated at 1920x1088, the converter should not be affected by this padding.