Wrap xe_pm_runtime_init inside xe_pm_init.

Cc: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Anshuman Gupta <anshuman.gupta@intel.com>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20230718080703.239343-3-anshuman.gupta@intel.comSigned-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>