kernel-tests: make recipe MACHINE-specific
kernel-tests: make recipe MACHINE-specific

These tests are by definition machine specific because we have
different kernels for different machines. Also the recipe contains
machine-specific override logic so make the recipe MACHINE-specific to
avoid feed errors because each machine rebuilds it under the feed
$arch dir.

Signed-off-by: Ioan-Adrian Ratiu <7ec73abcfe099fc5574c01312b62768070c80980@ni.com>

ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt,ni/meta-nilrt