clk: fixed-rate: Add clk flags for parent accuracy

Some clk providers want to use the accuracy of the parent clk and use
the fixed rate basic type clk to do that. This requires getting the
parent clk and extracting the accuracy before registering the fixed rate
clk. Let's add a flag for this and update the clk_ops to support this.

Cc: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Signed-off-by: Stephen Boyd <sboyd@kernel.org>
Link: https://lkml.kernel.org/r/20190830150923.259497-8-sboyd@kernel.org