net: bfin_mac: Remove unused stats member from struct bfin_mac_local

The bfin_mac driver keeps its statistics in net_device->stats, so the
stats member in struct bfin_mac_local is unused. Remove it, as well as
the accompanying comment.

Cc: adi-buildroot-devel@lists.sourceforge.net
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>