Add Chris as maintainer

I would like to help out on the reviews. I have been reviewing
occ-control code for over a year and I am ready to share some of the
maintanence burden going forward.

Here are my contributions to occ-control repository:
https://github.com/openbmc/openpower-occ-control/commits?author=cjcain

Change-Id: I4cb1d30ae6b9e7ce0eb2bebbbf156558245f93d4
Signed-off-by: Chris Cain <cjcain@us.ibm.com>
diff --git a/OWNERS b/OWNERS
index 92c2c72..08c50e1 100644
--- a/OWNERS
+++ b/OWNERS
@@ -33,6 +33,7 @@
 
 owners:
 - eajames@us.ibm.com
+- cjcain@us.ibm.com
 
 reviewers:
 
@@ -42,3 +43,6 @@
 - name: Eddie James
   email: eajames@us.ibm.com
   discord: eajames
+- name: Chris Cain
+  email: cjcain@us.ibm.com
+  discord: cjcain