drm/i915/display: rename intel_display_driver_* functions

Follow the usual naming conventions.

v2:
- Also rename references in comments (Gustavo)

Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/6ff7b76018bf4cf611037d7bf027c975cddfe2af.1681465222.git.jani.nikula@intel.com