docs(security): security advisory for CVE-2024-7881

Add CVE-2024-7881 security advisory document.

Signed-off-by: Arvind Ram Prakash <arvind.ramprakash@arm.com>
Change-Id: Ide976bc8754dc94d23e76001aaecf52556e7039a
diff --git a/docs/security_advisories/index.rst b/docs/security_advisories/index.rst
index 0ab73bc..a6fed96 100644
--- a/docs/security_advisories/index.rst
+++ b/docs/security_advisories/index.rst
@@ -17,3 +17,4 @@
    security-advisory-tfv-10.rst
    security-advisory-tfv-11.rst
    security-advisory-tfv-12.rst
+   security-advisory-tfv-13.rst