tools headers UAPI: Update tools's copy of drm/drm.h header

Picking the changes from:

  2e290c8d ("drm: document minimum kernel version for DRM_CLIENT_CAP_*")
  bbf4627b ("drm: clarify and linkify DRM_CLIENT_CAP_WRITEBACK_CONNECTORS docs")
  88938bf3

 ("drm: reference mode flags in DRM_CLIENT_CAP_* docs")

Silencing these perf build warnings:

  Warning: Kernel ABI header at 'tools/include/uapi/drm/drm.h' differs from latest version at 'include/uapi/drm/drm.h'
  diff -u tools/include/uapi/drm/drm.h include/uapi/drm/drm.h

No changes in tooling as these are just C comment documentation changes.

Cc: Simon Ser <contact@emersion.fr>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>