Platform/ARM/VExpressPkg: Make Dynamic Tables Framework default

The Dynamic Tables Framework enables unification of the firmware
for FVP_Base_AEMv8A-AEMv8A and FVP_Base_RevC-2xAEMv8A models such
that the same firmware binary can be used by these models.

Therefore, make Dynamic Tables Framework the default option for
building ACPI tables.

Signed-off-by: Sami Mujawar <sami.mujawar@arm.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>