libperf: Add pr_err() macro

And missing include for "perf/core.h" header, which provides LIBPERF_*
debug levels and add missing pr_err() support.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Alexey Budankov <alexey.budankov@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@linux.intel.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lore.kernel.org/lkml/20191017105918.20873-11-jolsa@kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/lib/include/perf/core.h

@@ -9,6 +9,7 @@
 #endif
 
 enum libperf_print_level {
+	LIBPERF_ERR,
 	LIBPERF_WARN,
 	LIBPERF_INFO,
 	LIBPERF_DEBUG,

tools/perf/lib/internal.h

@@ -2,6 +2,8 @@
 #ifndef __LIBPERF_INTERNAL_H
 #define __LIBPERF_INTERNAL_H
 
+#include <perf/core.h>
+
 void libperf_print(enum libperf_print_level level,
 		   const char *format, ...)
 	__attribute__((format(printf, 2, 3)));
@@ -11,6 +13,7 @@ do {                            \
 	libperf_print(level, "libperf: " fmt, ##__VA_ARGS__);     \
 } while (0)
 
+#define pr_err(fmt, ...)        __pr(LIBPERF_ERR, fmt, ##__VA_ARGS__)
 #define pr_warning(fmt, ...)    __pr(LIBPERF_WARN, fmt, ##__VA_ARGS__)
 #define pr_info(fmt, ...)       __pr(LIBPERF_INFO, fmt, ##__VA_ARGS__)
 #define pr_debug(fmt, ...)      __pr(LIBPERF_DEBUG, fmt, ##__VA_ARGS__)