ARM: ts4800: add ethernet support

This commit adds ethernet support to the TS4800. Note that the
MAC address is not fused on this board and have to be read from
FEC PALR PAUR registers (this is how the kernel provided by
Technologic Systems does it).

signed-off-by: Damien Riegel <damien.riegel@savoirfairelinux.com>
Cc: Stefano Babic <sbabic@denx.de>