clk: zynqmp: Fix divider calculation

clk: zynqmp: Fix divider calculation

Linux doesn't know maximum value of divisor that it can support.
zynqmp_clk_divider_round_rate() returns actual divider value
after calculating from parent rate and desired rate, even though
that rate is not supported by single divider of hardware. It is
also possible that such divisor value can be achieved through 2
different dividers. As, Linux tries to set such divisor value(out
of range) in single divider set divider is getting failed.

Fix the same by computing best possible combination of two
divisors which provides more accurate clock rate.

Signed-off-by: Rajan Vaja <rajan.vaja@xilinx.com>
Reviewed-by: Shubhrajyoti Datta <Shubhrajyoti.datta@xilinx.com>
Signed-off-by: Michal Simek <michal.simek@xilinx.com>