drm/i915/display: rename dev_priv -> i915 in crtc state dump

Rename dev_priv to i915 in crtc state dumping code.

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/3c1dafd45757d2de2e3f8404674168f2b1241170.1655372759.git.jani.nikula@intel.com