i386/tdx: Track mem_ptr for each firmware entry of TDVF

i386/tdx: Track mem_ptr for each firmware entry of TDVF

For each TDVF sections, QEMU needs to copy the content to guest
private memory via KVM API (KVM_TDX_INIT_MEM_REGION).

Introduce a field @mem_ptr for TdxFirmwareEntry to track the memory
pointer of each TDVF sections. So that QEMU can add/copy them to guest
private memory later.

TDVF sections can be classified into two groups:
 - Firmware itself, e.g., TDVF BFV and CFV, that located separately from
   guest RAM. Its memory pointer is the bios pointer.

 - Sections located at guest RAM, e.g., TEMP_MEM and TD_HOB.
   mmap a new memory range for them.

Register a machine_init_done callback to do the stuff.

Signed-off-by: Xiaoyao Li <xiaoyao.li@intel.com>
Acked-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Zhao Liu <zhao1.liu@intel.com>
Link: https://lore.kernel.org/r/20250508150002.689633-21-xiaoyao.li@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>