process-util: unify the hex value format a bit

And fix the man page reference as well.

src/basic/process-util.h

@@ -101,10 +101,10 @@ bool is_main_thread(void);
 bool oom_score_adjust_is_valid(int oa);
 
 #ifndef PERSONALITY_INVALID
-/* personality(7) documents that 0xffffffffUL is used for querying the
+/* personality(2) documents that 0xFFFFFFFFUL is used for querying the
  * current personality, hence let's use that here as error
  * indicator. */
-#define PERSONALITY_INVALID 0xffffffffLU
+#define PERSONALITY_INVALID 0xFFFFFFFFUL
 #endif
 
 /* The personality() syscall returns a 32-bit value where the top three bytes are reserved for flags that