Platform,Silicon/Qemu: Define PcdPcie*Limit variables

The ACPI tables require not only the base and the size
of various PCIe memory windows, but also the limit
defined as

Limit = Base + Size - 1

Given that ASL does not permit basic constant arithmetics when
defining resources or passing arguements to functions, we
define PCDs that hold these limits. The PCDs can then be modified
individually in platform DSC files.

Cc: Leif Lindholm <leif@nuviainc.com>
Cc: Ard Biesheuvel <ard.biesheuvel@arm.com>
Cc: Tanmay Jagdale <tanmay.jagdale@linaro.org>
Signed-off-by: Tomas Pilar <tomas@nuviateam.com>
Reviewed-by: Leif Lindholm <leif@nuviainc.com>