ArmPlatformPkg/PrePeiCore: seed temporary stack before entering PEI core
DEBUG builds of PEI code will print a diagnostic message regarding
the utilization of temporary RAM before switching to permanent RAM.
For example,
Total temporary memory: 16352 bytes.
temporary memory stack ever used: 4820 bytes.
temporary memory heap used for HobList: 4720 bytes.
Tracking stack utilization like this requires the stack to be seeded
with a known magic value, and this needs to occur before entering C
code, given that it uses the stack. Currently, only Nt32Pkg appears
to implement this feature, but it is useful nonetheless, so let's
wire it up for PrePeiCore.