spi-bcm2835: Disable forced software CS

Select software CS in bcm2708_common.dtsi, and disable the automatic
conversion in the driver to allow hardware CS to be re-enabled with an
overlay.

See: raspberrypi/linux#1547

Signed-off-by: Phil Elwell <phil@raspberrypi.org>

arch/arm/boot/dts/bcm2708_common.dtsi

@@ -183,7 +183,7 @@
 			 * add more gpios if necessary as <&gpio 6 1>
 			 * (but do not forget to make them output!)
 			 */
-			cs-gpios = <0>, <0>;
+			cs-gpios = <&gpio 8 1>, <&gpio 7 1>;
 		};
 
 		i2c0: i2c@7e205000 {

drivers/spi/spi-bcm2835.c

@@ -707,6 +707,7 @@ static int bcm2835_spi_setup(struct spi_device *spi)
 		return -EINVAL;
 	}
 
+#if 0
 	/* now translate native cs to GPIO */
 	/* first look for chip select pins in the devices pin groups */
 	for (pingroup_index = 0;
@@ -761,6 +762,7 @@ static int bcm2835_spi_setup(struct spi_device *spi)
 	 * so we are setting it here explicitly
 	 */
 	gpio_set_value(spi->cs_gpio, (spi->mode & SPI_CS_HIGH) ? 0 : 1);
+#endif
 
 	return 0;
 }