bnxt_en: Clean up completion ring page arrays completely

We recently changed the completion ring page arrays to be dynamically
allocated to better support the expanded range of ring depths.  The
cleanup path for this was not quite complete.  It might cause the
shutdown path to crash if we need to abort before the completion ring
arrays have been allocated and initialized.

Fix it by initializing the ring_mem->pg_arr to NULL after freeing the
completion ring page array.  Add a check in bnxt_free_ring() to skip
referencing the rmem->pg_arr if it is NULL.

Fixes: 03c74487 ("bnxt_en: Don't use static arrays for completion ring pages")
Reviewed-by: Andy Gospodarek <gospo@broadcom.com>
Reviewed-by: Edwin Peer <edwin.peer@broadcom.com>
Signed-off-by: Michael Chan <michael.chan@broadcom.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -2912,6 +2912,9 @@ static void bnxt_free_ring(struct bnxt *bp, struct bnxt_ring_mem_info *rmem)
 	struct pci_dev *pdev = bp->pdev;
 	int i;
 
+	if (!rmem->pg_arr)
+		goto skip_pages;
+
 	for (i = 0; i < rmem->nr_pages; i++) {
 		if (!rmem->pg_arr[i])
 			continue;
@@ -2921,6 +2924,7 @@ static void bnxt_free_ring(struct bnxt *bp, struct bnxt_ring_mem_info *rmem)
 
 		rmem->pg_arr[i] = NULL;
 	}
+skip_pages:
 	if (rmem->pg_tbl) {
 		size_t pg_tbl_size = rmem->nr_pages * 8;
 
@@ -3240,10 +3244,14 @@ static int bnxt_alloc_tx_rings(struct bnxt *bp)
 
 static void bnxt_free_cp_arrays(struct bnxt_cp_ring_info *cpr)
 {
+	struct bnxt_ring_struct *ring = &cpr->cp_ring_struct;
+
 	kfree(cpr->cp_desc_ring);
 	cpr->cp_desc_ring = NULL;
+	ring->ring_mem.pg_arr = NULL;
 	kfree(cpr->cp_desc_mapping);
 	cpr->cp_desc_mapping = NULL;
+	ring->ring_mem.dma_arr = NULL;
 }
 
 static int bnxt_alloc_cp_arrays(struct bnxt_cp_ring_info *cpr, int n)