virutil: Provide non-linux impl for virGetFCHostNameByFabricWWN

Currently, there's only linux implementation for
virGetFCHostNameByFabricWWN(). Since the symbol is exported in
our private symbols we ought to have implementation for other
platforms too. This also triggers compilation error on FreeBSD:

../src/.libs/libvirt_driver_storage_impl.a(libvirt_driver_storage_impl_la-storage_backend_scsi.o): In function `createVport':
/usr/home/jenkins/libvirt-master/systems/libvirt-freebsd/build/src/../../src/storage/storage_backend_scsi.c:740: undefined reference to `virGetFCHostNameByFabricWWN'
Signed-off-by: NMichal Privoznik <mprivozn@redhat.com>

src/util/virutil.c

@@ -2480,6 +2480,14 @@ virGetFCHostNameByWWN(const char *sysfs_prefix ATTRIBUTE_UNUSED,
     return NULL;
 }
 
+char *
+virGetFCHostNameByFabricWWN(const char *sysfs_prefix ATTRIBUTE_UNUSED,
+                            const char *fabric_wwn ATTRIBUTE_UNUSED)
+{
+    virReportSystemError(ENOSYS, "%s", _("Not supported on this platform"));
+    return NULL;
+}
+
 char *
 virFindFCHostCapableVport(const char *sysfs_prefix ATTRIBUTE_UNUSED)
 {