ptp: lan743x: remove .adjfreq implementation

The lan743x driver implements both .adjfreq and .adjfine, but the core PTP
subsystem prefers .adjfine if implemented. There is no reason to carry a
.adjfreq implementation, so we can remove it.

Signed-off-by: Jacob Keller <jacob.e.keller@intel.com>
Acked-by: Richard Cochran <richardcochran@gmail.com>
Cc: Bryan Whitehead <bryan.whitehead@microchip.com>
Cc: UNGLinuxDriver@microchip.com
Signed-off-by: David S. Miller <davem@davemloft.net>