spi: stm32_qspi: move to exec_op

We are facing issues in the driver since SPI NOR framework has moved
on SPI MEM framework, and SPI NAND framework is not running properly
with the current driver.

To be able to solve issues met on SPI NOR Flashes and to be able to
support SPI NAND Flashes, the driver has been reworked. We are now using
exec_op ops instead of using xfer ops.

Thanks to this rework, the driver has been successfully tested with:
 - mx66l51235l SPI NOR Flash on stm32f746 SOC
 - n25q128a SPI NOR Flash on stm32f769 SOC
 - mx66l51235l SPI NOR Flash on stm32mp1 SOC
 - mt29f2g01abagd SPI NAND Flash on stm32mp1 SOC
Signed-off-by: NChristophe Kerello <christophe.kerello@st.com>
Tested-by: NPatrick DELAUNAY <patrick.delaunay@st.com>
Reviewed-by: NPatrick DELAUNAY <patrick.delaunay@st.com>

drivers/spi/Kconfig

@@ -222,8 +222,7 @@ config SPI_SUNXI
 
 config STM32_QSPI
 	bool "STM32F7 QSPI driver"
-	depends on STM32F7
-	imply SPI_FLASH_BAR
+	depends on STM32F7 || ARCH_STM32MP
 	help
 	  Enable the STM32F7 Quad-SPI (QSPI) driver. This driver can be
 	  used to access the SPI NOR flash chips on platforms embedding