cpu: Provide a way to get the physical-address size

This concept exists on x86. Declare it as a generic function so that the
value can be accessed by UPL.

Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/arch/x86/lib/bdinfo.c b/arch/x86/lib/bdinfo.c
index 2a78f57..bd2cf0b 100644
--- a/arch/x86/lib/bdinfo.c
+++ b/arch/x86/lib/bdinfo.c
@@ -5,6 +5,7 @@
  * Copyright 2021 Google LLC
  */
 
+#include <cpu.h>
 #include <efi.h>
 #include <init.h>
 #include <asm/cpu.h>