zoom is actually a float value, don't convert to int

[simonschmeisser]

While looking at sailfishos/droidmedia#123 @b100dian noticed that my PR is superflous as this will actually be truncated here.

Functionality wise I still see steps in the zoom with the camera2 branch, will now cross verify with camera1

[simonschmeisser]

For camera1 api the zoom steps are much larger (44 vs 8.0) so this is not as noticeable

[b100dian]

That is a very good explanation 44 steps vs 8 (or 4 in my case)