clk/axs10x: Add I2S PLL clock driver

clk/axs10x: Add I2S PLL clock driver

The ARC SDP I2S clock can be programmed using a
specific PLL.

This patch has the goal of adding a clock driver
that programs this PLL.

At this moment the rate values are hardcoded in
a table but in the future it would be ideal to
use a function which determines the PLL values
given the desired rate.

Signed-off-by: Jose Abreu <joabreu@synopsys.com>
Acked-by: Rob Herring <robh@kernel.org>
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>