net: stmmac: boot KPI optimization

Avoid PHY reset when early Ethernet is enabled to save
atleast 90ms . Also, move Early Eth IP address assignment to
workqueue to save time taken in IP assignment.

Change-Id: Ifd04579894e93761eef2896596101dd17540e6a6
Signed-off-by: Suraj Jaiswal <jsuraj@codeaurora.org>