Fix wrong link in README

`OEM-IPMI Definitions` should link to `ipmi.md` instead of `ipmid.md`

Change-Id: I7b628812fffb4b06d0856ecc96207c59ed4818eb
Signed-off-by: Michael Shen <gpgpgp@google.com>
diff --git a/README.md b/README.md
index 26ff923..6983a8a 100644
--- a/README.md
+++ b/README.md
@@ -53,7 +53,7 @@
 
 ### IPMI Access to Phosphor-pid-control
 
-[OEM-IPMI Definitions](ipmid.md)
+[OEM-IPMI Definitions](ipmi.md)
 
 #### Set Sensor Value