arm: mvebu: a38x: serdes specification cleanup

arm: mvebu: a38x: serdes specification cleanup

Instead of allocating space in the driver for the serdes
specification table, just allow the board file to set a pointer
to it.  Also, allow the board to only specify the lanes that are
used instead of including unused lanes.

Signed-off-by: Kevin Smith <kevin.smith@elecsyscorp.com>
Acked-by: Stefan Roese <sr@denx.de>
Cc: Dirk Eibach <eibach@gdsys.de>
Cc: Luka Perkov <luka.perkov@sartura.hr>