perf hists: Fix up srcline histogram key formatting

perf hists: Fix up srcline histogram key formatting

Problem introduced in:

  commit 5b5916696051 "perf report: Honor column width setting"

Where the left justification signal was after the width, which ended up,
when the width was, say, 11, always printing:

	%11.11-s

Instead of src:line left justified and limited to 11 chars.

Resulting in a like:

    70.93%  %11.11-s  [.] f2                     tcall

When it should instead be:

    70.93%  tcall.c:5    [.] f2                     tcall

Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: David Ahern <dsahern@gmail.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Stephane Eranian <eranian@google.com>
Link: http://lkml.kernel.org/n/tip-2xnt0vqkoox52etq2qhyetr0@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>