configs: am62: Enable configs required for Ethboot

Enable config options needed to support Ethernet boot on AM62x SK.

Signed-off-by: Kishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: Siddharth Vadapalli <s-vadapalli@ti.com>
Signed-off-by: Chintan Vankar <c-vankar@ti.com>