perf c2c: Use stdio interface if slang is not supported

If the slang lib is not installed on the system, perf c2c tool disables TUI
mode and roll back to use stdio mode;  but the flag 'c2c.use_stdio' is
missed to set true and thus it wrongly applies UI quirks in the function
ui_quirks().

This commit forces to use stdio interface if slang is not supported, and
it can avoid to apply the UI quirks and show the correct metric header.

Before:

=================================================
      Shared Cache Line Distribution Pareto
=================================================
  -------------------------------------------------------------------------------
      0        0        0       99        0        0        0      0xaaaac17d6000
  -------------------------------------------------------------------------------
    0.00%    0.00%    6.06%    0.00%    0.00%    0.00%   0x20   N/A       0      0xaaaac17c25ac         0         0        43       375    18469         2  [.] 0x00000000000025ac  memstress         memstress[25ac]   0
    0.00%    0.00%   93.94%    0.00%    0.00%    0.00%   0x29   N/A       0      0xaaaac17c3e88         0         0       173       180      135         2  [.] 0x0000000000003e88  memstress         memstress[3e88]   0

After:

=================================================
      Shared Cache Line Distribution Pareto
=================================================
  -------------------------------------------------------------------------------
      0        0        0       99        0        0        0      0xaaaac17d6000
  -------------------------------------------------------------------------------
           0.00%    0.00%    6.06%    0.00%    0.00%    0.00%                0x20   N/A       0      0xaaaac17c25ac         0         0        43       375    18469         2  [.] 0x00000000000025ac  memstress         memstress[25ac]   0
           0.00%    0.00%   93.94%    0.00%    0.00%    0.00%                0x29   N/A       0      0xaaaac17c3e88         0         0       173       180      135         2  [.] 0x0000000000003e88  memstress         memstress[3e88]   0

Fixes: 5a1a99c ("perf c2c report: Add main TUI browser")
Reported-by: Joe Mario <jmario@redhat.com>
Signed-off-by: Leo Yan <leo.yan@linaro.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20220526145400.611249-1-leo.yan@linaro.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

Author: Leo Yan

tools/perf/builtin-c2c.c

@@ -2801,9 +2801,7 @@ static int perf_c2c__report(int argc, const char **argv)
 		   "the input file to process"),
 	OPT_INCR('N', "node-info", &c2c.node_info,
 		 "show extra node info in report (repeat for more info)"),
-#ifdef HAVE_SLANG_SUPPORT
 	OPT_BOOLEAN(0, "stdio", &c2c.use_stdio, "Use the stdio interface"),
-#endif
 	OPT_BOOLEAN(0, "stats", &c2c.stats_only,
 		    "Display only statistic tables (implies --stdio)"),
 	OPT_BOOLEAN(0, "full-symbols", &c2c.symbol_full,
@@ -2833,6 +2831,10 @@ static int perf_c2c__report(int argc, const char **argv)
 	if (argc)
 		usage_with_options(report_c2c_usage, options);
 
+#ifndef HAVE_SLANG_SUPPORT
+	c2c.use_stdio = true;
+#endif
+
 	if (c2c.stats_only)
 		c2c.use_stdio = true;