Add zhangkelvin@ as owner of fastboot

Working on replacing aio w/ liburing in fastboot recently

Change-Id: I8076e2e53dc8d620faf9bff7f37ba2d2538460d6
diff --git a/fastboot/OWNERS b/fastboot/OWNERS
index 17b3466..3dec07e 100644
--- a/fastboot/OWNERS
+++ b/fastboot/OWNERS
@@ -1,3 +1,5 @@
 dvander@google.com
 elsk@google.com
 enh@google.com
+zhangkelvin@google.com
+