rng-tools: Revert "rng-tools: move to meta-oe"

rng-tools: Revert "rng-tools: move to meta-oe"

This reverts commit d2b445384da3f3e6dab8577b6c56648b5244a788.

Revert this commit since:

 - some systems using oe-core master may still be using kernels from
   before 5.6 pulled in the rng-tools algorithm, and

 - some hardware platforms may not have a hardware random number generator
   and could therefore need to run rngd to avoid long boot-time initialization
   due to a depleted entropy pool.

Signed-off-by: Randy MacLeod <Randy.MacLeod@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>