arm: mvebu: clearfog: read number of ddr channels from tlv data

Extend the existing tlv vendor extension used for ram size by one byte to
also store the number of ddr channels.
The length of the tlv entry can indicate whether the new information is
present. If not default to single channel.

Signed-off-by: Josua Mayer <josua@solid-run.com>
Reviewed-by: Stefan Roese <sr@denx.de>