media: venus: Make debug infrastructure more flexible

Here we introduce debug prefixes for dev_dbg groups by level of
importance - Venus{Low,Med,High,FW} Enabling the particular level
will be done by dynamic debug.

For example to enable debug messages with low level:
echo 'format "VenusLow" +p' > debugfs/dynamic_debug/control

If you want to enable all levels:
echo 'format "Venus" +p' > debugfs/dynamic_debug/control

All the features which dynamic debugging provide are preserved.

Signed-off-by: Stanimir Varbanov <stanimir.varbanov@linaro.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>