examples/kni: fix dependency check for meson build

examples/kni: fix dependency check for meson build

Rather than hard-coding the example app to be built only when a set of
conditions are met, we can simplify things by having the app built when
KNI library itself is available. That saves us duplicating the same set
of restrictions on both library and example app.

Fixes: 89f0711f9ddf ("examples: build some samples with meson")

Signed-off-by: Bruce Richardson <bruce.richardson@intel.com>
Acked-by: Hemant Agrawal <hemant.agrawal@nxp.com>
Acked-by: Ferruh Yigit <ferruh.yigit@intel.com>