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>

tools/perf/builtin-c2c.c

@@ -1725,10 +1725,10 @@ static int c2c_hists__init_sort(struct perf_hpp_list *hpp_list, char *name)
 				tok; tok = strtok_r(NULL, ", ", &tmp)) {	\
 			ret = _fn(hpp_list, tok);				\
 			if (ret == -EINVAL) {					\
-				error("Invalid --fields key: `%s'", tok);	\
+				pr_err("Invalid --fields key: `%s'", tok);	\
 				break;						\
 			} else if (ret == -ESRCH) {				\
-				error("Unknown --fields key: `%s'", tok);	\
+				pr_err("Unknown --fields key: `%s'", tok);	\
 				break;						\
 			}							\
 		}								\