sdk: add spidev-test to the bundle of userspace sources

sdk: add spidev-test to the bundle of userspace sources

moves and extends the current facilities, which have been
added some time ago for the the usbip utility, to support
more utilites that are shipped with the Linux kernel tree
to the SDK.

this allows to drop all the hand-waving and code for
failed previous attempts to mitigate the SDK build failures.

Fixes: bdaaf66e28bd ("utils/spidev_test: build package directly from Linux")
Signed-off-by: Christian Lamparter <chunkeey@gmail.com>
(cherry picked from commit b479db9062b721776be44b976961a1031c1344ea)