net: phy: dp83822: Add support for changing the MAC termination

The dp83822 provides the possibility to set the resistance value of the
the MAC termination. Modifying the resistance to an appropriate value can
reduce signal reflections and therefore improve signal quality.

Reviewed-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
Signed-off-by: Dimitri Fedrau <dimitri.fedrau@liebherr.com>
Link: https://patch.msgid.link/20250416-dp83822-mac-impedance-v3-4-028ac426cddb@liebherr.com


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