[GIT FIXES FOR v4.2] Revert "[media] vb2: Push mmap_sem down to memops" & videodev2.h fix

Mauro, Please merge this revert asap. This patch introduces two serious regressions (first noticed when testing the cobalt driver, later reproduced with the vivid driver). This patch needs more work from Jan. Luckily I noticed in time and it should help Jan that it is reproducible with vivid, s

[GIT FIXES FOR v4.2] Revert "[media] vb2: Push mmap_sem down to memops"

Mauro, Please merge this revert asap. This patch introduces two serious regressions (first noticed when testing the cobalt driver, later reproduced with the vivid driver). This patch needs more work from Jan. Luckily I noticed in time and it should help Jan that it is reproducible with vivid, s