octeontx2-af: Fix uninitialized variable in debugfs

If rvu_get_blkaddr() fails, then this rvu_cgx_nix_cuml_stats() returns
zero and we write some uninitialized data into the debugfs output.

On the error paths, the use of the uninitialized "*stat" is harmless,
but it will lead to a Smatch warning (static analysis) and a UBSan
warning (runtime analysis) so we should prevent that as well.

Fixes: f967488d09 ("octeontx2-af: Add per CGX port level NIX Rx/Tx counters")
Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/marvell/octeontx2/af/rvu_cgx.c

@@ -608,6 +608,8 @@ int rvu_cgx_nix_cuml_stats(struct rvu *rvu, void *cgxd, int lmac_id,
 	u16 pcifunc;
 	int pf, lf;
 
+	*stat = 0;
+
 	if (!cgxd || !rvu)
 		return -EINVAL;
 
@@ -624,7 +626,6 @@ int rvu_cgx_nix_cuml_stats(struct rvu *rvu, void *cgxd, int lmac_id,
 		return 0;
 	block = &rvu->hw->block[blkaddr];
 
-	*stat = 0;
 	for (lf = 0; lf < block->lf.max; lf++) {
 		/* Check if a lf is attached to this PF or one of its VFs */
 		if (!((block->fn_map[lf] & ~RVU_PFVF_FUNC_MASK) == (pcifunc &