can: mcp25xxfd: mcp25xxfd_ring_free(): fix memory leak during cleanup

This loop doesn't free the first element of the array.  The "i > 0" has
to be changed to "i >= 0".

Fixes: 55e5b97f ("can: mcp25xxfd: add driver for Microchip MCP25xxFD SPI CAN")
Signed-off-by: NDan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20200923112752.GA1473821@mwandaSigned-off-by: NMarc Kleine-Budde <mkl@pengutronix.de>

drivers/net/can/spi/mcp25xxfd/mcp25xxfd-core.c

@@ -377,7 +377,7 @@ static void mcp25xxfd_ring_free(struct mcp25xxfd_priv *priv)
 {
 	int i;
 
-	for (i = ARRAY_SIZE(priv->rx) - 1; i > 0; i--) {
+	for (i = ARRAY_SIZE(priv->rx) - 1; i >= 0; i--) {
 		kfree(priv->rx[i]);
 		priv->rx[i] = NULL;
 	}