wifi: ath12k: initialize 'ret' in ath12k_dp_rxdma_ring_sel_config_wcn7850()

smatch flagged the following issue:

drivers/net/wireless/ath/ath12k/dp_rx.c:4065 ath12k_dp_rxdma_ring_sel_config_wcn7850() error: uninitialized symbol 'ret'.

In ath12k_dp_rxdma_ring_sel_config_wcn7850() if it were ever the case
that ab->hw_params->num_rxdma_per_pdev was 0 then 'ret' would be
uninitialized when it is returned. This should never be the case, but
to be safe and to quiet smatch, add an initializer to the declaration
of 'ret'.

No functional changes, compile tested only.

Signed-off-by: Jeff Johnson <quic_jjohnson@quicinc.com>
Signed-off-by: Kalle Valo <quic_kvalo@quicinc.com>
Link: https://msgid.link/20240504-ath12k_dp_rxdma_ring_sel_config_wcn7850-ret-v1-2-44d2843a2857@quicinc.com