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

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

The patch a557fca630cc: "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: a557fca630cc ("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.com
Signed-off-by: Mark Brown <broonie@kernel.org>