net/qcom emac: Assign MAC address based on availability

Current EMAC driver expect static MAC address and
return error if not present.

Add the support to initialize EMAC driver without static
MAC address.

Change-Id: If91e687cd313708653a86f83f478616c32e7724e
Signed-off-by: Alok Chauhan <alokc@codeaurora.org>