scripts/bloat-o-meter: fix python3 syntax error

In Python3+ print is a function so the old syntax is not correct
anymore:

  $ ./scripts/bloat-o-meter vmlinux.o vmlinux.o.old
    File "./scripts/bloat-o-meter", line 61
      print "add/remove: %s/%s grow/shrink: %s/%s up/down: %s/%s (%s)" % \
                                                                     ^
  SyntaxError: invalid syntax

Fix by calling print as a function.

Tested on python 2.7.11, 3.5.1

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>