clk: Support for clock parents and rates assigned from device tree

clk: Support for clock parents and rates assigned from device tree

This patch adds helper functions to configure clock parents and rates
as specified through 'assigned-clock-parents', 'assigned-clock-rates'
DT properties for a clock provider or clock consumer device.
The helpers are now being called by the bus code for the platform, I2C
and SPI busses, before the driver probing and also in the clock core
after registration of a clock provider.

Change-Id: I96d98c9c9d576fcbf0dfc90d1cc75feb9fdf97cb
Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
[s.nawrocki@samsung.com: backported to v3.10]
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mike Turquette <mturquette@linaro.org>