CVE-2023-53335

In the Linux kernel, the following vulnerability has been resolved:

RDMA/cxgb4: Fix potential null-ptr-deref in pass_establish()

If get_ep_from_tid() fails to lookup non-NULL value for ep, ep is
dereferenced later regardless of whether it is empty.
This patch adds a simple sanity check to fix the issue.

Found by Linux Verification Center (linuxtesting.org) with SVACE.