drm/i915/display: remove intel_display_commit_duplicated_state()

This seems like an unnecessary wrapper layer. Removing it will be
helpful later.

Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/a38f08e259221d71314ce6d764431147b0fba218.1681465222.git.jani.nikula@intel.com