spi: stm32-qspi: Fix stm32_qspi_transfer_one_message() error path

The patch a557fca6: "spi: stm32_qspi: Add transfer_one_message()
spi callback" from Aug 23, 2022, leads to the following Smatch static
checker warning:

drivers/spi/spi-stm32-qspi.c:627 stm32_qspi_transfer_one_message()
error: uninitialized symbol 'ret'.Fix the following Smatch static checker warning:

Fixes: a557fca6 ("spi: stm32_qspi: Add transfer_one_message() spi callback")
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Link: https://lore.kernel.org/r/20220826092031.1393430-1-patrice.chotard@foss.st.comSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-stm32-qspi.c

@@ -562,7 +562,7 @@ static int stm32_qspi_transfer_one_message(struct spi_controller *ctrl,
 	struct spi_transfer *transfer;
 	struct spi_device *spi = msg->spi;
 	struct spi_mem_op op;
-	int ret;
+	int ret = 0;
 
 	if (!spi->cs_gpiod)
 		return -EOPNOTSUPP;
@@ -592,8 +592,10 @@ static int stm32_qspi_transfer_one_message(struct spi_controller *ctrl,
 			dummy_bytes = transfer->len;
 
 			/* if happens, means that message is not correctly built */
-			if (list_is_last(&transfer->transfer_list, &msg->transfers))
+			if (list_is_last(&transfer->transfer_list, &msg->transfers)) {
+				ret = -EINVAL;
 				goto end_of_transfer;
+			}
 
 			transfer = list_next_entry(transfer, transfer_list);
 		}