Update the coverity exclusion file

Currently, no platform uses the libc strlcat function.

Change-Id: Idd0b1b999d211678cc03dc2d2bc5b506a0e23585
Signed-off-by: Madhukar Pappireddy <madhukar.pappireddy@arm.com>
diff --git a/script/tf-coverity/coverity_tf_conf.py b/script/tf-coverity/coverity_tf_conf.py
index 5be7c7d..392ad4a 100644
--- a/script/tf-coverity/coverity_tf_conf.py
+++ b/script/tf-coverity/coverity_tf_conf.py
@@ -52,6 +52,7 @@
 
     ("lib/compiler-rt/.*", "3rd party libraries will not be fixed"),
     ("lib/libfdt/.*", "3rd party libraries will not be fixed"),
+    ("lib/libc/strlcat.c", "Not used by any upstream platform"),
 
     ("tools/.*", "Host tools"),
 ]