net: phylink: Remove unused function pointer from phylink structure

From what I can tell the .get_fixed_state pointer in the phylink structure
hasn't been used since commit 5c05c1db ("net: phylink, dsa: eliminate
phylink_fixed_state_cb()") . Since I can't find any users for it we might
as well just drop the pointer.

Signed-off-by: Alexander Duyck <alexanderduyck@fb.com>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://patch.msgid.link/174240634772.1745174.5690351737682751849.stgit@ahduyck-xeon-server.home.arpa


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