Getting dbgfs help information with command "echo -help > vdec" or "echo > vdec". Signed-off-by: Yunfei Dong <yunfei.dong@mediatek.com> Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@collabora.com> Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl> Signed-off-by: Mauro Carvalho Chehab <mchehab@kernel.org>