Spreadtrum seth bindings

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

Required properties:
- compatible:
    - "sprd,seth": for network interface controller
    - "sprd,name": for name of nic
    - "sprd,dst": for id of destination
    - "sprd,channel": for id of channel
    - "sprd,blknum": for number of blocks
    - "sprd,poolsize": for the pool size of sipc