Ovmfpkg: update Ia32 build to use new work area

Ovmfpkg: update Ia32 build to use new work area

The commit 80e67af9afca added support for the generic work area concept
used mainly by the encrypted VMs. In the past, the work area was
preliminary used by the SEV-ES VMs. The SEV-ES support is available for
the X64 builds only. But now, that work area header contains fields that
nonencrypted VMs and SEV VMs can use. They can be built for IA32. So,
moving the work area defines outside of X64.

Fixes: 80e67af9afca ("OvmfPkg: introduce a common work area")
Cc: James Bottomley <jejb@linux.ibm.com>
Cc: Min Xu <min.m.xu@intel.com>
Cc: Jiewen Yao <jiewen.yao@intel.com>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Erdem Aktas <erdemaktas@google.com>
Cc: Gerd Hoffmann <kraxel@redhat.com>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Jiewen Yao <jiewen.yao@intel.com>