🍒 kcms/tablet: Improve calibration accuracy

The matrix we get from the calibration process should be multipled against the existing calibration matrix from the device, since it was used to create it in the first place. This also makes the refinement feature actually useful, because you can keep going and possibly get a more accurate calibration.

(cherry picked from commit fcb5af9b)

Co-authored-by: Joshua Goins josh@redstrate.com