drm/i915/pm: drop intel_pm_setup()

All the init in intel_pm_setup() is related to runtime pm. Move them to
intel_runtime_pm_init_early(), and remove intel_pm_setup().

Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/b01f9bf0afa9abaece5d0f76aecde69e2679f662.1677678803.git.jani.nikula@intel.com