drm/i915/display: remove unused for_each_crtc()

This is essentially a duplicate of drm_for_each_crtc() anyway. Remove.

Reviewed-by: Gustavo Sousa <gustavo.sousa@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20241202125437.1154945-1-jani.nikula@intel.com


Signed-off-by: Jani Nikula <jani.nikula@intel.com>