schemas: firmware: add MP2X6XXFirmware support

Add MP2X6XXFirmware support to I2CVRFirmware, which enables defining
firmware metadata for MP2X6XX voltage regulators.

In [1], support for updating MP2X6XX VR devices was introduced.

[1] https://gerrit.openbmc.org/c/openbmc/phosphor-bmc-code-mgmt/+/82113

Change-Id: I1fadf145d56c9ffbe4dea50913a273c54fde78f6
Signed-off-by: Kevin Tung <kevin.tung.openbmc@gmail.com>
diff --git a/schemas/firmware.json b/schemas/firmware.json
index 4fab42f..68706c9 100644
--- a/schemas/firmware.json
+++ b/schemas/firmware.json
@@ -28,7 +28,11 @@
                 },
                 "Type": {
                     "description": "The type of configuration object",
-                    "enum": ["XDPE1X2XXFirmware", "ISL69269Firmware"]
+                    "enum": [
+                        "XDPE1X2XXFirmware",
+                        "ISL69269Firmware",
+                        "MP2X6XXFirmware"
+                    ]
                 },
                 "Bus": {
                     "$ref": "legacy.json#/$defs/Types/Bus"