drm: Extract drm_connector.[hc]

Pulls in quite a lot of connector related structures (cmdline mode,
force/status enums, display info), but I think that all makes perfect
sense.

Also had to move a few more core kms object stuff into drm_modeset.h.

And as a first cleanup remove the kerneldoc for the 2 connector IOCTL
- DRM core docs are aimed at drivers, no point documenting internal in
excruciating detail.

v2: And also pull in all the connector property code.

Reviewed-by: Sean Paul <seanpaul@chromium.org>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1471034937-651-14-git-send-email-daniel.vetter@ffwll.ch