net: phy: Drop static phy_drivers list

net: phy: Drop static phy_drivers list

The static phy_drivers list is superseded by linker list of struct phy_drivers
now that all drivers have been converted to the later. Drop the phy_drivers
list as well as list_head from struct phy_driver.

Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
Reviewed-by: Ramon Fried <rfried.dev@gmail.com>
Acked-by: Michal Simek <michal.simek@amd.com>
Tested-by: Michal Simek <michal.simek@amd.com> #microblaze (MANUAL_RELOC)