net: zynq_gem: Update the MDC clock divisor in the probe function

MDC clock change needs to be done when the driver probe function
is called as mdio is enabled at probe and not when the ethernet starts.
Setup the MDC clock at the probe itself.

Signed-off-by: Venkatesh Yadav Abbarapu <venkatesh.abbarapu@amd.com>
Link: https://lore.kernel.org/r/20230922045010.22852-1-venkatesh.abbarapu@amd.com


Signed-off-by: Michal Simek <michal.simek@amd.com>