scripts/decode_stacktrace.sh: handle RIP address with segment

decode line:

  RIP: 0010:khugepaged+0x2a2/0x2280

into

  RIP: 0010:khugepaged (mm/khugepaged.c:1885)

Link: http://lkml.kernel.org/r/154660071227.52726.15645307951282727605.stgit@buzz


Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>