sfc: Remove more unused functions

sfc: Remove more unused functions

efx_ticks_to_usecs(), efx_reconfigure_port(), efx_ptp_get_mode(), and
efx_tx_get_copy_buffer_limited() are unused.
They seem to be partially due to the later splits to Siena, but
some seem unused for longer.

Remove them.

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Acked-by: Martin Habets <habetsm.xilinx@gmail.com>
Link: https://patch.msgid.link/20241102151625.39535-5-linux@treblig.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>