soc/tegra: pmc: Document tegra_pmc.syscore field

This eliminates a warning from the documentation build targets.

Signed-off-by: Thierry Reding <treding@nvidia.com>

drivers/soc/tegra/pmc.c

@@ -423,6 +423,7 @@ struct tegra_pmc_soc {
  * @wake_sw_status_map: Bitmap to hold raw status of wakes without mask
  * @wake_cntrl_level_map: Bitmap to hold wake levels to be programmed in
  *     cntrl register associated with each wake during system suspend.
+ * @syscore: syscore suspend/resume callbacks
  */
 struct tegra_pmc {
 	struct device *dev;