net/szedata2: refactor ibuf and obuf address definition

net/szedata2: refactor ibuf and obuf address definition

This is to prepare for firmwares with multiple ibufs and obufs.
Ibufs and obufs are the modules in FPGA firmware implementing
the Ethernet port.
There is one ibuf+obuf per Ethernet port.
The cards and firmwares allow one physical port to be one Ethernet
port or split into more Ethernet ports, e.g. one 100GE physical
port can be one Ethernet port of 100GE or split into ten Ethernet
ports of 10GE.
All DMA queues in the device are shared between all Ethernet ports.
Offsets of ibufs and obufs are defined in array.
Functions which operate on ibufs and obufs iterate over this array.

Signed-off-by: Matej Vido <vido@cesnet.cz>