[Convert] Support BGRx format for video.

[Convert] Support BGRx format for video.

Support BGRx in additional to RGB format.

How to test:

$ gst-launch-1.0 --gst-plugin-path=/source/AutoDrv/NNStreamer/convert2tensor/build videotestsrc ! video/x-raw,format=RGB,width=280,height=40,framerate=1/1 ! tee name=t ! queue ! videoconvert ! video/x-raw, format=BGRx ! convert2tensor ! filesink location="test.bgrx.log" sync=true t. ! queue ! filesink location="test.rgb.log" sync=true

If the resulting test.rgb.log has rgb format and test.bgrx.log has bgrx format, then it's good to go.

Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>