data-kernel: EMAC: Fix link speed issue after autoneg toggle

Advertise all supported speeds when autoneg is enabled.
Speed change is supported only when autoneg is disabled.
Add validation check for not supported half duplex mode.

Change-Id: Iea5ec04023d03ae3053d89c878174b3e2b8fec94
CRs-Fixed: 2264741
Acked-by: Rahul Kawadgave <rahulak@qti.qualcomm.com>
Signed-off-by: Sunil Paidimarri <hisunil@codeaurora.org>