soc/intel/elkhartlake: Enable 'scan_bus' on TSN GbE

For extern ethernet PHY access it is necessary to enable the 'scan_bus'
functionality.

Change-Id: I88050df2059ec7e0b27a132bca626eaef3d5dfb0
Signed-off-by: Mario Scheithauer <mario.scheithauer@siemens.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/69385
Reviewed-by: Werner Zeh <werner.zeh@siemens.com>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>

src/soc/intel/elkhartlake/tsn_gbe.c

@@ -135,6 +135,7 @@ static struct device_operations gbe_tsn_ops  = {
 	.read_resources   = pci_dev_read_resources,
 	.set_resources    = pci_dev_set_resources,
 	.enable_resources = pci_dev_enable_resources,
+	.scan_bus         = scan_generic_bus,
 	.enable           = gbe_tsn_enable,
 	.init             = gbe_tsn_init,
 };