dt-bindings: clk: Add Baikal-T1 CCU Dividers binding

dt-bindings: clk: Add Baikal-T1 CCU Dividers binding

After being gained by the CCU PLLs the signals must be transformed to
be suitable for the clock-consumers. This is done by a set of dividers
embedded into the CCU. A first block of dividers is used to create
reference clocks for AXI-bus of high-speed peripheral IP-cores of the
chip. The second block dividers alter the PLLs output signals to be then
consumed by SoC peripheral devices. Both block DT nodes are ordinary
clock-providers with standard set of properties supported. But in addition
to that each clock provider can be used to reset the corresponding clock
domain. This makes the AXI-bus and System Devices CCU DT nodes to be also
reset-providers.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: linux-mips@vger.kernel.org
Link: https://lore.kernel.org/r/20200526222056.18072-3-Sergey.Semin@baikalelectronics.ru
Reviewed-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>