Add script to automatically unzip newly installed kernels

Our uboot wants uncompressed kernels. Make sure this happens on kernel
package updates.
2 jobs for kernel-update in 1 minute and 58 seconds (queued for 2 seconds)
Status Name Job ID Coverage
  Build
passed build:deb #6490
librem5

00:01:29

passed build:docs #6489
librem5

00:01:58