cpu: add family default

Implementations need not provide the family information.

Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
Change-Id: I771e7d44ca41d7cc00602ec2b9411548b647e5e9
diff --git a/yaml/xyz/openbmc_project/Inventory/Item/Cpu.interface.yaml b/yaml/xyz/openbmc_project/Inventory/Item/Cpu.interface.yaml
index 7acf354..74f5671 100644
--- a/yaml/xyz/openbmc_project/Inventory/Item/Cpu.interface.yaml
+++ b/yaml/xyz/openbmc_project/Inventory/Item/Cpu.interface.yaml
@@ -12,6 +12,7 @@
           A free form string indicates processor family type.
           For example, values can be "Intel Xeon
           processor", "AS400 Family", etc.
+      default: ""
     - name: EffectiveFamily
       type: uint16
       description: >