include/device/device: add comment that config_of_soc never returns NULL

Since config_of() calls die() if dev or dev->chip_info are NULL,
config_of_soc() will either return a non-NULL pointer or won't return.

Change-Id: I6de6bb1610e823af215436c94ff1a78ff6b86b78
Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/48359
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Alexander Couzens <lynxis@fe80.eu>

src/include/device/device.h

@@ -385,6 +385,7 @@ static inline DEVTREE_CONST void *config_of(const struct device *dev)
 	devtree_die();
 }
 
+/* config_of_soc() either returns a non-NULL pointer or dies in the config_of() call. */
 static inline DEVTREE_CONST void *config_of_soc(void)
 {
 	return config_of(pcidev_on_root(0, 0));