tools include: Adopt PTR_ERR_OR_ZERO from the kernel err.h header

Add PTR_ERR_OR_ZERO, so that tools can use it, just like the kernel.
Signed-off-by: Ding Xiang <dingxiang@cmss.chinamobile.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1536284082-23466-1-git-send-email-dingxiang@cmss.chinamobile.comSigned-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/include/linux/err.h

@@ -52,4 +52,11 @@ static inline bool __must_check IS_ERR_OR_NULL(__force const void *ptr)
 	return unlikely(!ptr) || IS_ERR_VALUE((unsigned long)ptr);
 }
 
+static inline int __must_check PTR_ERR_OR_ZERO(__force const void *ptr)
+{
+	if (IS_ERR(ptr))
+		return PTR_ERR(ptr);
+	else
+		return 0;
+}
 #endif /* _LINUX_ERR_H */