Inventory.Item.Drive: add Capacity property

Capacity is one of the most important properties of storage device. Add
the property for storage drive interface to represent drive size in
bytes.

If size of the drive can't be determined, set Capacity to 0.

Signed-off-by: Andrei Kartashev <a.kartashev@yadro.com>
Change-Id: Ibb4662451bed19665557c26db3452576e588e667
diff --git a/yaml/xyz/openbmc_project/Inventory/Item/Drive.interface.yaml b/yaml/xyz/openbmc_project/Inventory/Item/Drive.interface.yaml
index 3460ed0..1b99f68 100644
--- a/yaml/xyz/openbmc_project/Inventory/Item/Drive.interface.yaml
+++ b/yaml/xyz/openbmc_project/Inventory/Item/Drive.interface.yaml
@@ -2,6 +2,11 @@
     Implement to provide drive attributes.
 
 properties:
+    - name: Capacity
+      default: 0
+      type: uint64
+      description: >
+          The size in bytes of the Drive. `0` if cannot be determined.
     - name: Type
       default: Unknown
       type: enum[self.DriveType]