ptp: clockmatrix: use rsmu driver to access i2c/spi bus

Backport of 930dfa56 from linux-stable.

rsmu (Renesas Synchronization Management Unit ) driver is located in
drivers/mfd and responsible for creating multiple devices including
clockmatrix phc, which will then use the exposed regmap and mutex
handle to access i2c/spi bus.

Signed-off-by: Min Li <min.li.xe@renesas.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Beniamin Sandu <beniamin.sandu@windriver.com>
Signed-off-by: Ruiqiang Hao <Ruiqiang.Hao@windriver.com>
Signed-off-by: Bruce Ashfield <bruce.ashfield@gmail.com>