drm: update drm.h to latest in drm-next.

This syncs the drm.h header with my drm-next branch as of
6d61e70ccc21606ffb8a0a03bd3aba24f659502b.

It brings over the semaphore API changes.

Generated using make headers_install.
Generated from git://people.freedesktop.org/~airlied/linux

 drm-next commit 6d61e70ccc2.

[airlied: I split patch in two, split reviewed by across both]

Reviewed-by: Eric Anholt <eric@anholt.net>
Signed-off-by: Dave Airlie <airlied@redhat.com>