Tiny fixes - resent

[Mario Kleiner]

Hi, a resend of updated versions of the earlier patches:

Patch 1 should really get into Linux 4.1 to avoid tegra breaking
user-space clients.

Patch 2 reviewed-by Michel, updated to take his feedback into account.

Patch 3 is modified to not conflict with Daniel Vetter's patch
"drm/vblank: Fixup and document timestamp update/read barriers"

Patch 4 will be needed for drm/qxl to compile with Daniel's fixup
patch applied.

thanks,
-mario