net: systemport: Add support for SYSTEMPORT Lite

Add supporf for the SYSTEMPORT Lite Ethernet controller, this piece of hardware
is largely based on the full-blown SYSTEMPORT and differs in the following:

- no full-blown UniMAC, instead we have the MagicPacket matching from UniMAC at
  same offset, and a GMII Interface Block (GIB) for the MAC-level stuff, since
  we are always interfaced to an Ethernet switch which is fully Ethernet compliant
  shortcuts could be made

- 16 transmit queues, whose interrupts are moved into the first Level-2 interrupt
  controller bank

- slight TDMA offset change (a register was inserted after TDMA_STATUS, *sigh*)

- 256 RX descriptors (512 words) and 256 TX descriptors (not visible)

As a consequence of these two things, update the code paths accordingly to
differentiate the full-blown from the light version.

Signed-off-by: Florian Fainelli <f.fainelli@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>