multimedia/makemkv: Update to 1.17.2

Changelog:

• Improved handling for discs with mastering errors
• Small improvements and bugfixes

Also drop DIST_SUBDIR as there are only two "extra" distfiles left, one
of them already shared with audio/fdk-aac, the other potentially shared
when multimedia/ffmpeg is updated.

Approved by: tcberner (mentor)
Differential Revision: https://reviews.freebsd.org/D37084