net: airoha: Add missing RX_CPU_IDX() configuration in airoha_qdma_cleanup_rx_queue()

net: airoha: Add missing RX_CPU_IDX() configuration in airoha_qdma_cleanup_rx_queue()

When the descriptor index written in REG_RX_CPU_IDX() is equal to the one
stored in REG_RX_DMA_IDX(), the hw will stop since the QDMA RX ring is
empty.
Add missing REG_RX_CPU_IDX() configuration in airoha_qdma_cleanup_rx_queue
routine during QDMA RX ring cleanup.

Fixes: 514aac359987 ("net: airoha: Add missing cleanup bits in airoha_qdma_cleanup_rx_queue()")
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Link: https://patch.msgid.link/20260408-airoha-cpu-idx-airoha_qdma_cleanup_rx_queue-v1-1-8efa64844308@kernel.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>