gpio: pca953x: Add support for PCA9556

PCA9556 is the software-compatible predecessor to the PCA9557, so add it
to the supported I2C device ID table.
Signed-off-by: NNate Case <ncase@xes-inc.com>
Cc: David Brownell <david-b@pacbell.net>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

drivers/gpio/pca953x.c

@@ -36,6 +36,7 @@ static const struct i2c_device_id pca953x_id[] = {
 	{ "pca9539", 16, },
 	{ "pca9554", 8, },
 	{ "pca9555", 16, },
+	{ "pca9556", 8, },
 	{ "pca9557", 8, },
 
 	{ "max7310", 8, },