genesys: Various fixes for GL841 scanners
This MR implements the following fixes and improvements:
- Fixed issue of motor becoming stuck at certain resolutions on Canon LiDE 50 and possibly other gl841 scanners (#357 (closed))
- Fixed incorrect LED exposure calculation leading to wrong color balance on certain resolutions on gl841 scanners
- Fixed gray scans to use white color for illumination instead of red on Canon LiDE 35/40/50/60 and potentially other gl841 scanners. Old behavior can be restored via the color filter setting to select specific color component for the gray scan.
- Fixed periodic black lines in gray scans on Canon LiDE 80.
- Improved scan quality on Canon LiDE 35/40/50/60 by using brighter LED illumination.
Fixes #357 (closed).
Edited by Povilas Kanapickas