Add tnagel to OWNERS

Thiemo has authored or reviewed many of the recent changes to this
repo and is also one of the most knowledgeable with regards to VPD
usage (especially outside factory/firmware team applications).

BUG=none
BRANCH=none
TEST=none

Change-Id: I21aa8c70b88c0ce0f6d3f6f9b54feef91b155932
Signed-off-by: David Hendricks <dhendrix@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/342583
Commit-Ready: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Hung-Te Lin <hungte@chromium.org>
Reviewed-by: Thiemo Nagel <tnagel@chromium.org>
diff --git a/OWNERS b/OWNERS
index 4d611d5..1dba7e3 100644
--- a/OWNERS
+++ b/OWNERS
@@ -1,3 +1,4 @@
 dhendrix@chromium.org
 hungte@chromium.org
+tnagel@chromium.org
 yjlou@chromium.org