spi: dw: fix crash on setup stage

The commit 1a7b7ee72c21 (spi: Ensure that CS line is in non-active state after
spi_setup()) introduces an unconditional call of spi_set_cs() before ->setup().
The dw_spi_set_cs() relies on that fact that ->setup() is already called, but
it doesn't now. This patch fixes the crash by adding an additional check to
dw_spi_set_cs().

Signed-off-by: Andy Shevchenko <[e-mail]>
Signed-off-by: Mark Brown <[e-mail]>

drivers/spi/spi-dw.c

···
 	struct chip_data *chip = spi_get_ctldata(spi);
 
 	/* Chip select logic is inverted from spi_set_cs() */
-	if (chip->cs_control)
+	if (chip && chip->cs_control)
 		chip->cs_control(!enable);
 
 	if (!enable)