scripts/bloat-o-meter: don't fail with division by 0

Under some circumstances it's possible to get a divider 0 which crashes
the script.

  Traceback (most recent call last):
    File "linux/scripts/bloat-o-meter", line 98, in <module>
      print_result("Function", "tTdDbBrR", 2)
    File "linux/scripts/bloat-o-meter", line 87, in print_result
      (otot, ntot, (ntot - otot)*100.0/otot))
  ZeroDivisionError: float division by zero

Hide this by checking the divider first.

Link: http://lkml.kernel.org/r/20171123171219.31453-1-andriy.shevchenko@linux.intel.com


Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Cc: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Vaneet Narang <v.narang@samsung.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>