ospack: Ship rngd on all the images, not just minimal

With newer kernels it takes far longer in early boot to get random
numbers (as >= 4.18 kernels ensure good quality entropy is availble
before starting  providing randomness).

Commit 85cc6eba took care of the minimal ospack/images introducing
rng-tools to integrate with hardware random number generators
while jitterentropy-rngd can provide randomness without.

This commit applies the same change to the target, basesdk and sdk
ospacks/images.

Signed-off-by: Emanuele Aina <emanuele.aina@collabora.com>