drm/xe: fix build warning with CONFIG_PM=n

The 'runtime_status' field is an implementation detail of the
power management code, so a device driver should not normally
touch this:

drivers/gpu/drm/xe/xe_pm.c: In function 'xe_pm_suspending_or_resuming':
drivers/gpu/drm/xe/xe_pm.c:606:26: error: 'struct dev_pm_info' has no member named 'runtime_status'
  606 |         return dev->power.runtime_status == RPM_SUSPENDING ||
      |                          ^
drivers/gpu/drm/xe/xe_pm.c:607:27: error: 'struct dev_pm_info' has no member named 'runtime_status'
  607 |                 dev->power.runtime_status == RPM_RESUMING;
      |                           ^
drivers/gpu/drm/xe/xe_pm.c:608:1: error: control reaches end of non-void function [-Werror=return-type]

Add an #ifdef check to avoid the build regression.

Fixes: cb85e39 ("drm/xe: Suppress missing outer rpm protection warning")
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@intel.com>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Link: https://patchwork.freedesktop.org/patch/msgid/20240909202521.1018439-1-arnd@kernel.org
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

drivers/gpu/drm/xe/xe_pm.c

@@ -601,10 +601,14 @@ bool xe_pm_runtime_get_if_in_use(struct xe_device *xe)
  */
 static bool xe_pm_suspending_or_resuming(struct xe_device *xe)
 {
+#ifdef CONFIG_PM
 	struct device *dev = xe->drm.dev;
 
 	return dev->power.runtime_status == RPM_SUSPENDING ||
 		dev->power.runtime_status == RPM_RESUMING;
+#else
+	return false;
+#endif
 }
 
 /**