net: stmmac: dwmac-qcom-ethqos: Use max frequency for clk_ptp_ref

Qualcomm clocks can set their frequency to a variety of levels
generally. Let's use the max for clk_ptp_ref to ensure the best
timestamping resolution possible.

Without this, the default value of the clock is used. For sa8775p-ride
this is 19.2 MHz, far less than the 230.4 MHz possible.

Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Andrew Halaney <ahalaney@redhat.com>
Link: https://lore.kernel.org/r/20230725211853.895832-4-ahalaney@redhat.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>