MLK-20755: mxc-jpeg: gst-launch only shows the first frame of an yu422 video

Make sure V4L2_EVENT_SOURCE_CHANGE is only sent at init phase.
It was wrongly sent for every frame, causing gst-launch to DQBUF
only for the first frame.

Removed a dev_dbg from mxc_jpeg_try_fmt, too many prints with gst.

Fix for "Driver bug detected, stride (%d) is too small for the width (%d)"
warning in gst-launch. Fixed by providing the stride in bytesperline, in
mxc_jpeg_g_fmt_vid_cap function.

Clean-up in mxc_jpeg_qbuf.

Tested with gst-launch and v4l2video0jpegdec plugin:
gst-launch-1.0 filesrc location=mjpeg_64x64_4frames.avi ! jpegparse
	! v4l2video0jpegdec ! waylandsink

Signed-off-by: Mirela Rabulea <mirela.rabulea@nxp.com>