drivers/spi: stm32: fix warning in SYS_LOG_ERR macro

Following log subsystem rework, a warning poped-up in SYS_LOG_ERR
in spi_stm32_get_err macro.
Fix it by casting SPI_STM32_ERR_MSK on (u32_t)

Fixes #10380

Signed-off-by: Erwan Gouriou <erwan.gouriou@linaro.org>
1 file changed