Merge branch 'octeon_ep_vf-fix-napi_build_skb-null-dereference'

David Carlier says:

====================
octeon_ep_vf: fix napi_build_skb() NULL dereference

napi_build_skb() can return NULL on allocation failure. In
__octep_vf_oq_process_rx(), the result is used directly without a
NULL check in both the single-buffer and multi-fragment paths,
leading to a NULL pointer dereference.

Patch 1 introduces a helper to deduplicate the ring index advance
pattern, patch 2 adds the actual NULL checks.
====================

Link: https://patch.msgid.link/20260409184009.930359-1-devnexen@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>