Revert "perf report: Add warning when libunwind not compiled in"

BugLink: https://bugs.launchpad.net/bugs/1858798

This reverts commit 800d3f56 upstream.

This commit introduces a build failure in tools/perf on environments
that don't have libunwind installed.

[...]
builtin-report.c: In function ‘report__setup_sample_type’:
builtin-report.c:289:6: error: ‘dwarf_callchain_users’ undeclared (first
use in this function)
  if (dwarf_callchain_users) {
      ^
[...]

The variable 'dwarf_callchain_users' was introduced by eabad8c6
"perf unwind: Do not look just at the global callchain_param.record_mode"
which as of now hasn't been backported to stable linux-4.4.y. So revert
this commit to fix the build failure.
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>
Acked-by: Stefan Bader <stefan.bader@canonical.com>
Acked-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>

tools/perf/builtin-report.c

@@ -285,13 +285,6 @@ static int report__setup_sample_type(struct report *rep)
 				PERF_SAMPLE_BRANCH_ANY))
 		rep->nonany_branch_mode = true;
 
-#ifndef HAVE_LIBUNWIND_SUPPORT
-	if (dwarf_callchain_users) {
-		ui__warning("Please install libunwind development packages "
-			    "during the perf build.\n");
-	}
-#endif
-
 	return 0;
 }