i2c: muxes: pca954x: update list of supported devices

The Kconfig help has not been updated while adding PCA9547 and PCA9646.

Signed-off-by: Luca Ceresoli <luca@lucaceresoli.net>
Acked-by: Michal Simek <michal.simek@xilinx.com>
Reviewed-by: Heiko Schocher<hs@denx.de>
diff --git a/drivers/i2c/muxes/Kconfig b/drivers/i2c/muxes/Kconfig
index b0da67c..4a601c8 100644
--- a/drivers/i2c/muxes/Kconfig
+++ b/drivers/i2c/muxes/Kconfig
@@ -29,11 +29,11 @@
 	tristate "TI PCA954x I2C Mux/switches"
 	depends on I2C_MUX
 	help
-	  If you say yes here you get support for the TI PCA954x
-	  I2C mux/switch devices. It is x width I2C multiplexer which enables to
-	  partitioning I2C bus and connect multiple devices with the same address
-	  to the same I2C controller where driver handles proper routing to
-	  target i2c device. PCA9544 and PCA9548 are supported.
+	  If you say yes here you get support for the TI PCA954x I2C mux/switch
+	  devices. It is x width I2C multiplexer which enables to partitioning
+	  I2C bus and connect multiple devices with the same address to the same
+	  I2C controller where driver handles proper routing to target i2c
+	  device. Supported chips are PCA9544, PCA9547, PCA9548 and PCA9646.
 
 config I2C_MUX_GPIO
         tristate "GPIO-based I2C multiplexer"