OWNERS: Add Nikhil Ashoka

I propose myself (Nikhil Ashoka) as a maintainer.
These are my commits so far:
https://gerrit.openbmc.org/q/owner:a.nikhil@ibm.com

Signed-off-by: Nikhil Ashoka <a.nikhil@ibm.com>
Change-Id: If3f4f0709cd567494c9dfbeb17a88dde526e09d7
diff --git a/OWNERS b/OWNERS
index 8398b5f..0f2dec3 100644
--- a/OWNERS
+++ b/OWNERS
@@ -34,9 +34,9 @@
 owners:
 - gunnar@gmills.xyz
 - kirankumarb@ami.com
+- a.nikhil@ibm.com
 
 reviewers:
-- a.nikhil@ibm.com
 - jwestover@nvidia.com
 - sivaprabug@ami.com