i2c: mux: reg: Provide of_match_table

of_match_table was not filled which prevents device to be
instantiated from device tree node.

Signed-off-by: Lukasz Gemborowski <lukasz.gemborowski@nokia.com>
Reviewed-by: Alexander Sverdlin <alexander.sverdlin@nokia.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>