vexpress64: use DM for all vexpress64 boards

vexpress64: use DM for all vexpress64 boards

Commit d8bafe1310487ba0e0785997726b4792072178d3
"ARMv8: enable DM in vexpress64 board" only enabled DM
for the simulated vexpress64 board (FVP) with the
hardcoded clock value for the simulated board, causing
a console regression on the Juno board which was using
a different clock setting.

Fix this by enabling DM for all vexpress64 boards,
defining the clock frequency per-board, deleting the
static array of PL01x ports from the config file and
relying solely on the port defined in the boardfile
using platform data.

Cc: David Feng <fenghua@phytium.com.cn>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>