Add an amplitude limiting filter for the variable qual

[Vayne-Lover]

Hello
When i do some experiments recently i notice that though the quality of picture is high,the variable qual still jitters.In order to avoid the jitter,i add an amplitude limiting filter.And after that the analyse look like smooth when it is stable.
First picture before change:

Second picture before change:

First picture After change:

Second picture After change:

[AlexisTM]

I think this filtering is done on the PX4 Firmware side.