perf script: Finish the rename from trace to script

The scripts have calls to 'perf trace' that need to be converted to 'perf script', do it.

This problem was introduced in 133dc4c.

Reported-by: Torok Edwin <edwintorok@gmail.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Ingo Molnar <mingo@elte.hu>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Tom Zanussi <tzanussi@gmail.com>
Cc: Torok Edwin <edwintorok@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

tools/perf/scripts/perl/rw-by-file.pl

@@ -18,7 +18,7 @@ use lib "./Perf-Trace-Util/lib";
 use Perf::Trace::Core;
 use Perf::Trace::Util;
 
-my $usage = "perf trace -s rw-by-file.pl <comm>\n";
+my $usage = "perf script -s rw-by-file.pl <comm>\n";
 
 my $for_comm = shift or die $usage;