Rename host-ipmid/files to host-ipmid/host-ipmid

In preparation for additional recipes in this directory.
diff --git a/common/recipes-phosphor/host-ipmid/files/host-ipmid.service b/common/recipes-phosphor/host-ipmid/host-ipmid/host-ipmid.service
similarity index 100%
rename from common/recipes-phosphor/host-ipmid/files/host-ipmid.service
rename to common/recipes-phosphor/host-ipmid/host-ipmid/host-ipmid.service