fix wrong typo

Signed-off-by: Jerry Yu <jerry.h.yu@arm.com>
diff --git a/.travis.yml b/.travis.yml
index 3b1d705..a97a3c2 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -101,7 +101,7 @@
         - programs/test/selftest
         - tests/scripts/test_psa_constant_names.py
         # Modern OpenSSL does not support fixed ECDH or null ciphers.
-        - tests/compat.sh -p OpenSSL -e 'NULL\|ECDH-'
+        - tests/compat.sh -p OpenSSL -e 'NULL\|ECDH_'
         - tests/scripts/travis-log-failure.sh
         - tests/context-info.sh