schemas: firmware: add MP994XFirmware support

Add MP994XFirmware support to I2CVRFirmware, which enables defining
firmware metadata for MP994X voltage regulators.

In [1], support for updating MP994X VR devices was introduced.

[1] https://gerrit.openbmc.org/c/openbmc/phosphor-bmc-code-mgmt/+/84278

Tested with a dummy config.

Change-Id: I3fc4f772b866ece944bc289ff79cffb58b278994
Signed-off-by: Kevin Tung <kevin.tung.openbmc@gmail.com>
diff --git a/schemas/firmware.json b/schemas/firmware.json
index b6b4254..7be83bd 100644
--- a/schemas/firmware.json
+++ b/schemas/firmware.json
@@ -51,6 +51,7 @@
                         "MP2X6XXFirmware",
                         "MP297XFirmware",
                         "MP5998Firmware",
+                        "MP994XFirmware",
                         "RAA22XGen2Firmware",
                         "RAA22XGen3p5Firmware"
                     ]