[media] tvp5150: don't go past decoder->input_ent array

drivers/media/i2c/tvp5150.c:1394 tvp5150_parse_dt() warn: buffer overflow 'decoder->input_ent' 3 <= 3

Reviewed-by: Javier Martinez Canillas <javier@osg.samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@osg.samsung.com>