i2c-gpio: Fix adapter number

It turns out that platform_device.id is a "u32" so testing it for being
nonnegative is useless when setting up an i2c bitbang device. Instead,
do what the platform_bus code does and test it against the value "-1".

Signed-off-by: David Brownell <[e-mail]>
Acked-by: Atsushi Nemoto <[e-mail]>
Signed-off-by: Jean Delvare <[e-mail]>

drivers/i2c/busses/i2c-gpio.c

···
 	 * The reason to do so is to avoid sysfs names that only make
 	 * sense when there are multiple adapters.
 	 */
-	adap->nr = pdev->id >= 0 ? pdev->id : 0;
+	adap->nr = (pdev->id != -1) ? pdev->id : 0;
 	ret = i2c_bit_add_numbered_bus(adap);
 	if (ret)
 		goto err_add_bus;