tracing: Fix mmiotrace possible NULL dereferencing of hiter->dev

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UBUNTU-CVE-2026-68176

In the Linux kernel, the following vulnerability has been resolved: tracing: Fix mmiotrace possible NULL dereferencing of hiter-dev If the mmiopipeopen fails to find a PCI device, the hiter-dev will be assigned to NULL. The mmiotrace read function dereferences the hiter-dev if hiter exists. Chang...