drivers: spi: stm32 spi driver using ll_func as defined in the header
drivers: spi: stm32 spi driver using ll_func as defined in the header

Instead of checking the SPI register flags, the spi_ll_stm32.h
has dedicated functions for that purpose.
They are abstracting the STM32 registers of SPI instance.

Signed-off-by: Francois Ramu <b83adc7f8a23ee911a37fcb61c4033581aae0b7a@st.com>

galak/zephyr,finikorg/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,finikorg/zephyr,galak/zephyr,finikorg/zephyr,zephyrproject-rtos/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,zephyrproject-rtos/zephyr,galak/zephyr,galak/zephyr