gpio-pca953x: fix gpio_base

gpio_base was set to 0 if no system platform data or open firmware
platform data was provided. This led to conflicts, if any other gpiochip
with a gpiobase of 0 was instantiated already. Setting it to -1 will
automatically use the first one available.

Signed-off-by: Hartmut Knaack <[e-mail]>
Signed-off-by: Grant Likely <[e-mail]>

drivers/gpio/gpio-pca953x.c

···
 void
 pca953x_get_alt_pdata(struct i2c_client *client, int *gpio_base, int *invert)
 {
+	*gpio_base = -1;
 }
 #endif