dev-tools: Add jitterentropy-rngd

This works around the RNG issue linux-emcraft#2 causing SSH logins to
be inaccessible for five minutes on boot.  With this package, SSH is
available immediately.
1 job from add-jitterentropy-rngd in 49 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #6570
librem5
build-debian-package

00:00:49