add support for PCA9547

This MR adds support for the PCA9547 I2C MUX.

PCA9547 MUX is almost identical to the already implemented PCA9548A, as a result, the code is basically a copy of the PCA9548A implementation.

The only difference made in the code is the selection of channels: in PCA9548A, the selection of one channel is done by setting one of 8 bits to high; in PCA9547, the selection of one channel out of 8 channels is done by 3 bits (i.e. an internal decoder is there).

The datasheet is here: https://www.nxp.com/docs/en/data-sheet/PCA9547.pdf