phy: zynqmp: Allow variation in refclk rate

Due to limited available frequency ratios, the reference clock rate may
not be exactly the same as the required rate. Allow a small (100 ppm)
deviation.

Signed-off-by: Sean Anderson <sean.anderson@seco.com>
Link: https://lore.kernel.org/r/20230711194542.898230-1-sean.anderson@seco.com
Signed-off-by: Vinod Koul <vkoul@kernel.org>