perf tools: Improve aux_output not supported error

For example:

 Before:
   $ perf record -e '{intel_pt/branch=0/,branch-loads/aux-output/ppp}' -- ls -l
   Error:
   branch-loads: PMU Hardware doesn't support sampling/overflow-interrupts. Try 'perf stat'

 After:
   $ perf record -e '{intel_pt/branch=0/,branch-loads/aux-output/ppp}' -- ls -l
   Error:
   branch-loads: PMU Hardware doesn't support 'aux_output' feature

Signed-off-by: Adrian Hunter <adrian.hunter@intel.com>
Reviewed-by: Andi Kleen <ak@linux.intel.com>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Link: http://lore.kernel.org/lkml/20200710151104.15137-4-adrian.hunter@intel.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>