perf annotate: Calculate the max instruction name, align column to that

perf annotate: Calculate the max instruction name, align column to that

We were hardcoding '6' as the max instruction name, and we have lots
that are longer than that, see the diff from two 'P' printed TUI
annotations for a libc function that uses instructions with long names,
such as 'vpmovmskb' with its 9 chars:

  --- __strcmp_avx2.annotation.before	2019-03-06 16:31:39.368020425 -0300
  +++ __strcmp_avx2.annotation	2019-03-06 16:32:12.079450508 -0300
  @@ -2,284 +2,284 @@
   Event: cycles:ppp

   Percent        endbr64
  -  0.10         mov    %edi,%eax
  +  0.10         mov        %edi,%eax
  -               xor    %edx,%edx
  +               xor        %edx,%edx
  -  3.54         vpxor  %ymm7,%ymm7,%ymm7
  +  3.54         vpxor      %ymm7,%ymm7,%ymm7
  -               or     %esi,%eax
  +               or         %esi,%eax
  -               and    $0xfff,%eax
  +               and        $0xfff,%eax
  -               cmp    $0xf80,%eax
  +               cmp        $0xf80,%eax
  -             ↓ jg     370
  +             ↓ jg         370
  - 27.07         vmovdqu (%rdi),%ymm1
  + 27.07         vmovdqu    (%rdi),%ymm1
  -  7.97         vpcmpeqb (%rsi),%ymm1,%ymm0
  +  7.97         vpcmpeqb   (%rsi),%ymm1,%ymm0
  -  2.15         vpminub %ymm1,%ymm0,%ymm0
  +  2.15         vpminub    %ymm1,%ymm0,%ymm0
  -  4.09         vpcmpeqb %ymm7,%ymm0,%ymm0
  +  4.09         vpcmpeqb   %ymm7,%ymm0,%ymm0
  -  0.43         vpmovmskb %ymm0,%ecx
  +  0.43         vpmovmskb  %ymm0,%ecx
  -  1.53         test   %ecx,%ecx
  +  1.53         test       %ecx,%ecx
  -             ↓ je     b0
  +             ↓ je         b0
  -  5.26         tzcnt  %ecx,%edx
  +  5.26         tzcnt      %ecx,%edx
  - 18.40         movzbl (%rdi,%rdx,1),%eax
  + 18.40         movzbl     (%rdi,%rdx,1),%eax
  -  7.09         movzbl (%rsi,%rdx,1),%edx
  +  7.09         movzbl     (%rsi,%rdx,1),%edx
  -  3.34         sub    %edx,%eax
  +  3.34         sub        %edx,%eax
     2.37         vzeroupper
                ← retq
                  nop
  -         50:   tzcnt  %ecx,%edx
  +         50:   tzcnt      %ecx,%edx
  -               movzbl 0x20(%rdi,%rdx,1),%eax
  +               movzbl     0x20(%rdi,%rdx,1),%eax
  -               movzbl 0x20(%rsi,%rdx,1),%edx
  +               movzbl     0x20(%rsi,%rdx,1),%edx
  -               sub    %edx,%eax
  +               sub        %edx,%eax
                  vzeroupper
                ← retq
  -               data16 nopw %cs:0x0(%rax,%rax,1)
  +               data16     nopw %cs:0x0(%rax,%rax,1)

Reported-by: Travis Downs <travis.downs@gmail.com>
LPU-Reference: CAOBGo4z1KfmWeOm6Et0cnX5Z6DWsG2PQbAvRn1MhVPJmXHrc5g@mail.gmail.com
Cc: Adrian Hunter <adrian.hunter@intel.com>
Cc: Jiri Olsa <jolsa@kernel.org>
Cc: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/n/tip-89wsdd9h9g6bvq52sgp6d0u4@git.kernel.org
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>