spi: spi-synquacer: fix set_cs handling

When the slave chip select is deasserted, DMSTOP bit
must be set.

Fixes: b0823ee35cf9 ("spi: Add spi driver for Socionext SynQuacer platform")
Signed-off-by: Masahisa Kojima <[e-mail]>
Signed-off-by: Jassi Brar <[e-mail]>
Cc: [e-mail]
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Mark Brown <[e-mail]>

drivers/spi/spi-synquacer.c

···
 	val &= ~(SYNQUACER_HSSPI_DMPSEL_CS_MASK <<
 		 SYNQUACER_HSSPI_DMPSEL_CS_SHIFT);
 	val |= spi->chip_select << SYNQUACER_HSSPI_DMPSEL_CS_SHIFT;
+
+	if (!enable)
+		val |= SYNQUACER_HSSPI_DMSTOP_STOP;
+
 	writel(val, sspi->regs + SYNQUACER_HSSPI_REG_DMSTART);
 }