Revert "vexpress64: fvp dram: add DRAM configuration"

This reverts commit fc04b923 where the
FVP DRAM configuration was added.

Signed-off-by: Ryan Harkin <ryan.harkin@linaro.org>
Acked-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Sudeep Holla <sudeep.holla@arm.com>