i2c: muxes: pca954x: Allow sharing reset GPIO

Some hardware designs with multiple PCA954x devices use a reset GPIO
connected to all the muxes. Support this configuration by making use of
the reset controller framework which can deal with the shared reset
GPIOs. Fall back to the old GPIO descriptor method if the reset
controller framework is not enabled.

Signed-off-by: Chris Packham <chris.packham@alliedtelesis.co.nz>
Acked-by: Peter Rosin <peda@axentia.se>
Reviewed-by: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Signed-off-by: Wolfram Sang <wsa+renesas@sang-engineering.com>