MLK-21153-1 spi: lpspi: fix the dataloss when slave is in PIO mode

Related issues have been fixed by (e0e542ae MLK-20060-1 spi: lpspi:
fix wrong transmission when don't use CONT). However, the delay between
sending and receiving in slave mode. This causes the value of
FSR_RXCOUNT cannot reflect whether there is still data not sent timely.
So do this judgement by FSR_TXCOUNT.

Signed-off-by: Clark Wang <xiaoning.wang@nxp.com>
(cherry picked from commit 1a260d13aa3724b9919a2d8e2f53b4ad26ccf372)

drivers/spi/spi-fsl-lpspi.c

@@ -77,6 +77,7 @@
 #define CFGR1_NOSTALL	BIT(3)
 #define CFGR1_MASTER	BIT(0)
 #define FSR_RXCOUNT	(0xFF << 16)
+#define FSR_TXCOUNT	(0xFF)
 #define RSR_RXEMPTY	BIT(1)
 #define TCR_CPOL	BIT(31)
 #define TCR_CPHA	BIT(30)
@@ -758,7 +759,7 @@ static irqreturn_t fsl_lpspi_isr(int irq, void *dev_id)
 	}
 
 	if (temp_SR & SR_MBF ||
-	    readl(fsl_lpspi->base + IMX7ULP_FSR) & FSR_RXCOUNT) {
+	    readl(fsl_lpspi->base + IMX7ULP_FSR) & FSR_TXCOUNT) {
 		writel(SR_FCF, fsl_lpspi->base + IMX7ULP_SR);
 		fsl_lpspi_intctrl(fsl_lpspi, IER_FCIE);
 		return IRQ_HANDLED;