clk: berlin: drop direct of_iomap of nodes reg property

The Berlin clock driver was sharing a DT node with the pin controller
and the reset driver. All these devices are now sub-nodes of the chip
controller. This patch rework the Berlin clock driver to allow moving
the Berlin clock DT bindings into their own sub-node of the chip
controller node.

Signed-off-by: Antoine Tenart <antoine.tenart@free-electrons.com>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>