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>
1 file changed