OvmfPkg/RiscVVirt: Add Stack HOB

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=4350



Currently, stack HOB is not created for the stack memory. This causes
stack memory to be treated as free memory and any memory allocation which
happens at this address causes random memory corruption. Fix this by
creating the stack HOB which marks the memory as BS data.

Cc: Liming Gao <gaoliming@byosoft.com.cn>
Cc: Andrei Warkentin <andrei.warkentin@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
Reported-by: Andrei Warkentin <andrei.warkentin@intel.com>
Tested-by: Andrei Warkentin <andrei.warkentin@intel.com>
Reviewed-by: Andrei Warkentin <andrei.warkentin@intel.com>