spi: stm32: clear only asserted irq flags on interrupt

Previously the stm32h7 interrupt thread cleared all non-masked interrupts.
If an interrupt was to occur during the handling of another interrupt its
flag would be unset, resulting in a lost interrupt.
This patches fixes the issue by clearing only the currently set interrupt
flags.
Signed-off-by: Tobias Schramm <t.schramm@manjaro.org>
Link: https://lore.kernel.org/r/20200804195136.1485392-1-t.schramm@manjaro.orgSigned-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-stm32.c

@@ -966,7 +966,7 @@ static irqreturn_t stm32h7_spi_irq_thread(int irq, void *dev_id)
 		if (!spi->cur_usedma && (spi->rx_buf && (spi->rx_len > 0)))
 			stm32h7_spi_read_rxfifo(spi, false);
 
-	writel_relaxed(mask, spi->base + STM32H7_SPI_IFCR);
+	writel_relaxed(sr & mask, spi->base + STM32H7_SPI_IFCR);
 
 	spin_unlock_irqrestore(&spi->lock, flags);