net: stmmac: add support to read mac address from oem fuse

The driver gets efuse address from device tree property.
It then read mac address 6 bytes from this address and
validates it. If the address is valid it is saved for
future use as appropriate.

Change-Id: Ic25183a7834182cf6671dca2f96431c70fd936ee
Signed-off-by: Rishi Gupta <rishgupt@codeaurora.org>