device: introduce and use dev_get_domain_id

To avoid having constructs like 'dev->path.domain.domain' in the SoC
code, create the 'dev_get_domain_id' helper function that returns the
domain ID of either that device if it's a domain device or the
corresponding domain device's domain ID, and use it in the code.

If this function is called with a device other than PCI or domain type,
it won't have a domain number. In order to not need to call 'die',
'dev_get_domain_id' will print an error and return 0 which is a valid
domain number. In that case, the calling code should be fixed.

Signed-off-by: Felix Held <felix-coreboot@felixheld.de>
Change-Id: I3d79f19846cea49609f848a4c42747ac1052c288
Reviewed-on: https://review.coreboot.org/c/coreboot/+/83644
Reviewed-by: Shuo Liu <shuo.liu@intel.com>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/include/device/device.h

@@ -183,6 +183,7 @@ const char *dev_name(const struct device *dev);
 const char *dev_path(const struct device *dev);
 u32 dev_path_encode(const struct device *dev);
 const struct device *dev_get_domain(const struct device *dev);
+unsigned int dev_get_domain_id(const struct device *dev);
 void dev_set_enabled(struct device *dev, int enable);
 void disable_children(struct bus *bus);
 bool dev_is_active_bridge(struct device *dev);