x86/p2m: restrict auditing to debug builds

... since iterating through all of a guest's pages may take unduly
long.

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

--- a/xen/include/asm-x86/p2m.h
+++ b/xen/include/asm-x86/p2m.h
@@ -600,7 +600,11 @@ int set_p2m_entry(struct p2m_domain *p2m
 extern void p2m_pt_init(struct p2m_domain *p2m);
 
 /* Debugging and auditing of the P2M code? */
+#ifndef NDEBUG
 #define P2M_AUDIT     1
+#else
+#define P2M_AUDIT     0
+#endif
 #define P2M_DEBUGGING 0
 
 #if P2M_AUDIT