src/poky:systemtap: correctly set include location for the python module

This issue was as well exposed by setting S to be in UNPACKDIR.

(From OE-Core rev: a9b8cd548bc4f12b7aa28209d7c04181c95b7e7a)

Signed-off-by: Alexander Kanavin <alexlinutronix.de>
Signed-off-by: Mathieu Dubois-Briand <mathieu.dubois-briandbootlin.com>
Signed-off-by: Richard Purdie <richard.purdielinuxfoundation.org>

Author: kanavin