net: stmmac: move stmmac_check_ether_addr() to driver probe

stmmac_check_ether_addr() checks the MAC address and assigns one in
driver open(). In many cases when we create slave netdevice, the dev
addr is inherited from master but the master dev addr maybe NULL at
that time, so move this call to driver probe so that address is
always valid.

Signed-off-by: Xiaofei Shen <xiaofeis@codeaurora.org>
Tested-by: Xiaofei Shen <xiaofeis@codeaurora.org>
Signed-off-by: Sneh Shah <snehshah@codeaurora.org>
Signed-off-by: Vinod Koul <vkoul@kernel.org>
Reviewed-by: Andrew Lunn <andrew@lunn.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>