Fix license description in README.chromium.

The license file in srtp/LICENSE is a standard 3-clause BSD license.
Fix the License: field to say so, to satisfy the WebView license
checker.

BUG=
R=mnaganov@chromium.org
TBR=brettw@chromium.org

Review URL: https://codereview.chromium.org/156553003

git-svn-id: http://src.chromium.org/svn/trunk/deps/third_party/libsrtp@250757 4ff67af0-8c30-449e-8e8b-ad334ec8d88c
diff --git a/README.chromium b/README.chromium
index 24aa060..f1c9335 100644
--- a/README.chromium
+++ b/README.chromium
@@ -1,7 +1,7 @@
 Name: libsrtp
 URL: http://srtp.sourceforge.net/srtp.html
 Version: 1.4.4
-License: BSD-based license
+License: 3-clause BSD
 License File: srtp/LICENSE
 Security Critical: Yes