net: phy: dp83867: Add support for MAC impedance configuration

Add support for programmable MAC impedance configuration and
fix typo in DT impedance parameters names.

Signed-off-by: Mugunthan V N <mugunthanvnm@ti.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Tested-by: Lokesh Vutla <lokeshvutla@ti.com>
Acked-by: Joe Hershberger <joe.hershberger@ni.com>