spi: spi-stm32-qspi: Remove CR_FTHRES_MASK usage

On STM32 F4/F7/H7 SoCs, FTHRES is a 5 bits field in QSPI_CR register,
but for STM32MP1 SoCs, FTHRES is a 4 bits field long. CR_FTHRES_MASK
definition is not correct.

As for all these SoCs, FTHRES field is set to 3, FIELD_PREP() macro
is used with a constant as second parameter which make its usage useless.

CR_FTHRES_MASK and FIELD_PREP() can be removed.

Signed-off-by: Patrice Chotard <patrice.chotard@st.com>
Signed-off-by: Mark Brown <broonie@kernel.org>
diff --git a/drivers/spi/spi-stm32-qspi.c b/drivers/spi/spi-stm32-qspi.c
index 42f8e3c..5dbb6a8 100644
--- a/drivers/spi/spi-stm32-qspi.c
+++ b/drivers/spi/spi-stm32-qspi.c
@@ -29,7 +29,7 @@
 #define CR_SSHIFT		BIT(4)
 #define CR_DFM			BIT(6)
 #define CR_FSEL			BIT(7)
-#define CR_FTHRES_MASK		GENMASK(12, 8)
+#define CR_FTHRES_SHIFT		8
 #define CR_TEIE			BIT(16)
 #define CR_TCIE			BIT(17)
 #define CR_FTIE			BIT(18)
@@ -463,7 +463,7 @@ static int stm32_qspi_setup(struct spi_device *spi)
 	flash->presc = presc;
 
 	mutex_lock(&qspi->lock);
-	qspi->cr_reg = FIELD_PREP(CR_FTHRES_MASK, 3) | CR_SSHIFT | CR_EN;
+	qspi->cr_reg = 3 << CR_FTHRES_SHIFT | CR_SSHIFT | CR_EN;
 	writel_relaxed(qspi->cr_reg, qspi->io_base + QSPI_CR);
 
 	/* set dcr fsize to max address */