drm/i915: reduce includes in intel_clock_gating.c
With the refactoring in the file, some excessive includes were left
behind and are now unnecessary. Remove.
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20240530100747.328631-2-jani.nikula@intel.com
Signed-off-by: Jani Nikula <jani.nikula@intel.com>