gpio: mcp23s08: Bug fix of SPI device tree registration.

The chips variable needs to be incremented for each chip that is
found in the spi_present_mask when registering via device tree.
Without this and the checking a negative index is passed to the
data->chip array in a subsequent loop.

Cc: stable@vger.kernel.org
Signed-off-by: Michael Welling <mwelling@ieee.org>
Acked-by: Peter Korsgaard <peter@korsgaard.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>

drivers/gpio/gpio-mcp23s08.c

@@ -894,9 +894,11 @@ static int mcp23s08_probe(struct spi_device *spi)
 			dev_err(&spi->dev, "invalid spi-present-mask\n");
 			return -ENODEV;
 		}
-
-		for (addr = 0; addr < ARRAY_SIZE(pdata->chip); addr++)
+		for (addr = 0; addr < ARRAY_SIZE(pdata->chip); addr++) {
+			if ((spi_present_mask & (1 << addr)))
+				chips++;
 			pullups[addr] = 0;
+		}
 	} else {
 		type = spi_get_device_id(spi)->driver_data;
 		pdata = dev_get_platdata(&spi->dev);
@@ -919,12 +921,12 @@ static int mcp23s08_probe(struct spi_device *spi)
 			pullups[addr] = pdata->chip[addr].pullups;
 		}
 
-		if (!chips)
-			return -ENODEV;
-
 		base = pdata->base;
 	}
 
+	if (!chips)
+		return -ENODEV;
+
 	data = kzalloc(sizeof(*data) + chips * sizeof(struct mcp23s08),
 			GFP_KERNEL);
 	if (!data)