Unisoc sipa-eth bindings

This is only for virtual network interface controller that dealing with ipa data transferring.

Required properties:
- compatible: Must be "sprd,sipa_eth".
- sprd,netid: index for SIPA NIC interface
- sprd,term-type: names for the various IPA srouce / destination ID
- sprd,mac-header: a bool to indicate a skb has to pull its mac header or not

Example:

aliases {
	eth0 = &sipa_eth0;
	...
	eth8 = &sipa_eth8;
};

sipa_eth8:  sipa-wifi {
	compatible = "sprd,sipa_eth";
	sprd,netid = <0>;
	sprd,term-type = <0x2>;
};

On Roc1+Orca platform:
sipa_eth0: sipa-eth0 {
	compatible = "sprd,sipa_eth";
	sprd,netid = <1>;
	sprd,term-type = <0x6>;
};

On Orca CPE platform:
sipa_eth0: sipa-eth0 {
	compatible = "sprd,sipa_eth";
	sprd,netid = <1>;
	sprd,term-type = <0x6>;
	sprd,mac-header;
};
