perf tools: Replace error() with pr_err()

To consolidate the error reporting facility.

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/n/tip-b41iot1094katoffdf19w9zk@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
diff --git a/tools/perf/builtin-kmem.c b/tools/perf/builtin-kmem.c
index 9409c94..0a8a1c4 100644
--- a/tools/perf/builtin-kmem.c
+++ b/tools/perf/builtin-kmem.c
@@ -1715,7 +1715,7 @@
 		if (!tok)
 			break;
 		if (slab_sort_dimension__add(tok, sort_list) < 0) {
-			error("Unknown slab --sort key: '%s'", tok);
+			pr_err("Unknown slab --sort key: '%s'", tok);
 			free(str);
 			return -1;
 		}
@@ -1741,7 +1741,7 @@
 		if (!tok)
 			break;
 		if (page_sort_dimension__add(tok, sort_list) < 0) {
-			error("Unknown page --sort key: '%s'", tok);
+			pr_err("Unknown page --sort key: '%s'", tok);
 			free(str);
 			return -1;
 		}