perf annotate: Do not truncate instruction names at 6 chars

perf annotate: Do not truncate instruction names at 6 chars

There are many instructions, esp on PowerPC, whose mnemonics are longer
than 6 characters. Using precision limit causes truncation of such
mnemonics.

Fix this by removing precision limit. Note that, 'width' is still 6, so
alignment won't get affected for length <= 6.

Before:

   li     r11,-1
   xscvdp vs1,vs1
   add.   r10,r10,r11

After:

  li     r11,-1
  xscvdpsxds vs1,vs1
  add.   r10,r10,r11

Reported-by: Donald Stence <dstence@us.ibm.com>
Signed-off-by: Ravi Bangoria <ravi.bangoria@linux.vnet.ibm.com>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Taeung Song <treeze.taeung@gmail.com>
Link: http://lkml.kernel.org/r/20171114032540.4564-1-ravi.bangoria@linux.vnet.ibm.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>