ArmPlatformPkg: remove ArmJuno.dsc/fdf

ArmPlatformPkg: remove ArmJuno.dsc/fdf

ARM Ltd Platform support is migrating to use OpenPlatformPkg [1].

Currently, Juno exists both in EDK2's ArmPlatformPkg and in
OpenPlatformPkg [2].  And they are starting to diverge, with
OpenPlatformPkg being the most up-to-date with current developments.
To prevent this divergence, remove the .dsc and .fdf files from
ArmPlatformPkg and leave OpenPlatformPkg as the master.

We can't remove ArmJuno.dec yet because ACPI still uses it to set the
include path to ArmPlatform.h.

[1] https://git.linaro.org/uefi/OpenPlatformPkg.git
[2] https://git.linaro.org/uefi/OpenPlatformPkg.git/tree/master:/Platforms/ARM/Juno

Contributed-under: TianoCore Contribution Agreement 1.0
Signed-off-by: Ryan Harkin <ryan.harkin@linaro.org>