i40e: Remove unused i40e_(read|write)_phy_register

i40e: Remove unused i40e_(read|write)_phy_register

i40e_read_phy_register() and i40e_write_phy_register() were added in
2016 by
commit f62ba91458b5 ("i40e: Add functions which apply correct PHY access
method for read and write operation")

but haven't been used.

Remove them.

(There are more specific _clause* variants of these functions
that are still used.)

Signed-off-by: Dr. David Alan Gilbert <linux@treblig.org>
Reviewed-by: Tony Nguyen <anthony.l.nguyen@intel.com>
Link: https://patch.msgid.link/20250102173717.200359-4-linux@treblig.org
Signed-off-by: Jakub Kicinski <kuba@kernel.org>