bnxt_en: Fix allocation of zero statistics block size regression.

Recent commit added logic to determine the appropriate statistics block
size to allocate and the size is stored in bp->hw_ring_stats_size. But
if the firmware spec is older than 1.6.0, it is 0 and not initialized.
This causes the allocation to fail with size 0 and bnxt_open() to
abort. Fix it by always initializing bp->hw_ring_stats_size to the
legacy default size value.

Fixes: 4e7485066373 ("bnxt_en: Allocate the larger per-ring statistics block for 57500 chips.")
Reported-by: Jonathan Lemon <[e-mail]>
Signed-off-by: Michael Chan <[e-mail]>
Tested-by: Jonathan Lemon <[e-mail]>
Acked-by: Jonathan Lemon <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/ethernet/broadcom/bnxt/bnxt.c

···
 	struct hwrm_vnic_qcaps_input req = {0};
 	int rc;
 
+	bp->hw_ring_stats_size = sizeof(struct ctx_hw_stats);
 	if (bp->hwrm_spec_code < 0x10600)
 		return 0;
 
···
 		if (bp->max_tpa_v2)
 			bp->hw_ring_stats_size =
 				sizeof(struct ctx_hw_stats_ext);
-		else
-			bp->hw_ring_stats_size = sizeof(struct ctx_hw_stats);
 	}
 	mutex_unlock(&bp->hwrm_cmd_lock);
 	return rc;