drm/i915/lvds: s/dev_priv/i915/

Do the customary s/dev_priv/i915/ rename and aliasing
'dev' pointer removal. Though various register definitions
still depend on the magic 'dev_priv' variable so not
a 100% conversion.
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230130180540.8972-7-ville.syrjala@linux.intel.comReviewed-by: Jani Nikula <jani.nikula@intel.com>