perf report: Fix no libunwind compiled warning break s390 issue

perf report: Fix no libunwind compiled warning break s390 issue

Commit 800d3f561659 ("perf report: Add warning when libunwind not
compiled in") breaks the s390 platform. S390 uses libdw-dwarf-unwind for
call chain unwinding and had no support for libunwind.

So the warning "Please install libunwind development packages during the
perf build." caused the confusion even if the call-graph is displayed
correctly.

This patch adds checking for HAVE_DWARF_SUPPORT, which is set when
libdw-dwarf-unwind is compiled in.

Fixes: 800d3f561659 ("perf report: Add warning when libunwind not compiled in")
Signed-off-by: Jin Yao <yao.jin@linux.intel.com>
Reviewed-by: Thomas Richter <tmricht@linux.ibm.com>
Tested-by: Thomas Richter <tmricht@linux.ibm.com>
Acked-by: Jiri Olsa <jolsa@redhat.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Jin Yao <yao.jin@intel.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lore.kernel.org/lkml/20200107191745.18415-1-yao.jin@linux.intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>