drm/i915/lvds: Rename intel_lvds to intel_lvds_encoder

In preparation for introducing intel_lvds_connector to move some of the
LVDS specific storage away from drm_i915_private, first rename the encoder
to avoid potential confusion.

Based on earlier work by Chris Wilson <chris@chris-wilson.co.uk>

CC: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>
Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>