reader: set correct subsampled width for 1080i2997
reader: set correct subsampled width for 1080i2997

Limecraft/ebu-libmxf,ebu/ebu-libmxf,stuarthicks/libmxf,stuarthicks/libmxf,ebu/ebu-libmxf,stuarthicks/libmxf,ebu/ebu-libmxf,ebu/ebu-libmxf,stuarthicks/libmxf,Limecraft/ebu-libmxf,Limecraft/ebu-libmxf