gst/mxf/: Some random cleanup.

gst/mxf/: Some random cleanup.

Original commit message from CVS:
* gst/mxf/mxfalaw.c: (mxf_is_alaw_essence_track):
* gst/mxf/mxfalaw.h:
* gst/mxf/mxfdemux.c:
(gst_mxf_demux_handle_header_metadata_update_streams):
* gst/mxf/mxfjpeg2000.c: (mxf_is_jpeg2000_essence_track):
* gst/mxf/mxfjpeg2000.h:
* gst/mxf/mxfmpeg.c: (mxf_is_mpeg_essence_track),
(mxf_mpeg_es_create_caps), (mxf_mpeg_create_caps):
* gst/mxf/mxfmpeg.h:
Some random cleanup.