dt-bindings: net: ti: cpsw: switch to use phy-gmii-sel phy

The cpsw-phy-sel driver was replaced with new PHY driver phy-gmii-sel, so
deprecate cpsw-phy-sel bindings and update CPSW binding to use phy-gmii-sel
PHY bindings.

Cc: Kishon Vijay Abraham I <kishon@ti.com>
Cc: Tony Lindgren <tony@atomide.com>
Signed-off-by: Grygorii Strashko <grygorii.strashko@ti.com>
Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>