net: phylink: convert phylink_mii_c22_pcs_config() to neg_mode

Use phylink_pcs_neg_mode() for phylink_mii_c22_pcs_config(). This
results in no functional change.

Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Link: https://lore.kernel.org/r/E1qA8Dj-00EaFG-Mt@rmk-PC.armlinux.org.uk
Signed-off-by: Jakub Kicinski <kuba@kernel.org>