net: airoha: Do not store hfwd references in airoha_qdma struct

Since hfwd descriptor and buffer queues are allocated via
dmam_alloc_coherent() we do not need to store their references
in airoha_qdma struct. This patch does not introduce any logical changes,
just code clean-up.

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250521-airopha-desc-sram-v3-2-a6e9b085b4f0@kernel.org


Signed-off-by: Paolo Abeni <pabeni@redhat.com>