drm/xe/compat: remove intel_runtime_pm.h

Now that all display code has been converted to display specific runtime
PM interfaces, there's no need for the compat header anymore.

Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Link: https://lore.kernel.org/r/037ed1f38c96715c76514e9eb7069b896ce06ba1.1742483007.git.jani.nikula@intel.com