avfilter/vf_lenscorrection: get rid of some floats
avfilter/vf_lenscorrection: get rid of all floats per frame

there are some still left for 1 time initialization

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
avfilter/vf_lenscorrection: get rid of floats in init code

The only remaining floats are in the user interface, they are left as they
should not cause a problem in practice

Signed-off-by: Michael Niedermayer <michaelni@gmx.at>