State: add new RebootCause value for supporting Software reset

According new design from below commit:
https://gerrit.openbmc.org/c/openbmc/docs/+/73678

We need to add new `RebootCause` value for Software reset.

Tested:
busctl get-property xyz.openbmc_project.State.BMC \
/xyz/openbmc_project/state/bmc0 xyz.openbmc_project.State.BMC \
LastRebootCause

When executing reboot command then return as below:
s "xyz.openbmc_project.State.BMC.BMCResetCause.Software"

Signed-off-by: Tim Lee <timlee660101@gmail.com>
Change-Id: Iaeadc05960556aec09acd65bf0253c7267786dd7
diff --git a/yaml/xyz/openbmc_project/State/BMC.interface.yaml b/yaml/xyz/openbmc_project/State/BMC.interface.yaml
index 5dbc2f7..d25e573 100644
--- a/yaml/xyz/openbmc_project/State/BMC.interface.yaml
+++ b/yaml/xyz/openbmc_project/State/BMC.interface.yaml
@@ -80,6 +80,9 @@
           - name: "Watchdog"
             description: >
                 Last reboot is caused by Watchdog
+          - name: "Software"
+            description: >
+                Last reboot is caused by Software
           - name: "Unknown"
             description: >
                 Last reboot is caused by Unknown