net: openvswitch: fix possible kfree_skb of ERR_PTR

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CVE-2024-56778

CVE-2024-56778 affects the Linux kernel DRM STI driver. The root cause is that sti_hqvdp_atomic_check could dereference an error pointer because the return value of drm_atomic_get_crtc_state() was not checked, risking invalid pointer use and potential instability. The vulnerability is limited to ...