ksum.py: python -> python3

ksum.py: python -> python3

* Testinfo:
  In kernel's builddir:
  $ /path/to/oe-core/scripts/tiny/ksum.py

Collecting object files [DONE]

Totals:

vmlinux:
    text        data            bss             total
    10933110    3824470         1605632         16363212

modules (2004):
    text        data            bss             total
    46144408    3047516         167580          49359504

vmlinux + modules:
    text        data            bss             total
    57077518    6871986         1773212         65722716

Signed-off-by: Robert Yang <liezhi.yang@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>