OvmfPkg/SmbiosPlatformDxe: clean up #includes and INF

- Sort all sections in the INF file.

- Remove unused packages (MdeModulePkg) and lib classes (BaseMemoryLib)
  from the INF file.

- Restrict some lib classes (BaseLib, HobLib) and GUIDs (gEfiXenInfoGuid)
  to IA32 and X64, in the INF file; only the IA32/X64 Xen implementation
  requires these.

- Don't make "SmbiosPlatformDxe.h" #include everything just as a
  convenience. Spell out directly needed #includes in every file (annotate
  each with an example identifier consumed), drop unused #includes.

- Keep #includes sorted.

- Remove the leading underscore from the #include guard macro name in
  "SmbiosPlatformDxe.h".

Cc: Anthony Perard <anthony.perard@citrix.com>
Cc: Ard Biesheuvel <ardb+tianocore@kernel.org>
Cc: Jordan Justen <jordan.l.justen@intel.com>
Cc: Julien Grall <julien@xen.org>
Cc: Philippe Mathieu-Daudé <philmd@redhat.com>
Ref: https://bugzilla.tianocore.org/show_bug.cgi?id=2122
Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Message-Id: <20210526201446.12554-37-lersek@redhat.com>
Reviewed-by: Ard Biesheuvel <ardb@kernel.org>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>

OvmfPkg/SmbiosPlatformDxe/X86Xen.c

@@ -8,9 +8,11 @@
 
 **/
 
+#include <Library/BaseLib.h> // AsciiStrnCmp()
+#include <Library/HobLib.h>  // GetFirstGuidHob()
+#include <Pi/PiHob.h>        // EFI_HOB_GUID_TYPE
+
 #include "SmbiosPlatformDxe.h"
-#include <Library/HobLib.h>
-#include <Guid/XenInfo.h>
 
 #define XEN_SMBIOS_PHYSICAL_ADDRESS       0x000EB000
 #define XEN_SMBIOS_PHYSICAL_END           0x000F0000