s5k3l6xx: Support staging driver

By fixing format setting and implementing (as a stub) a link frequency control.
2 jobs for formats2 in 75 minutes and 6 seconds (queued for 32 seconds)
Status Job ID Name Coverage
  Build
passed #367096
librem5
build:aarch64

00:16:44

passed #367097
librem5:arm64
build:deb

01:09:24