In commit fd8ee93c3a38 ("UBUNTU: [Packaging] drop useless linux-doc") we
decided to remove the linux-doc package, saving in this way a lot of
space required to produce the documentation content (that can be easily
found online).
However, this change broke some user-space packages that are still
requiring linux-doc as a dependency.
Therefore, re-introduce an empty linux-doc package to prevent the
breakgage and at the same time avoid to re-introduce the expensive build
dependencies.
Signed-off-by: Andrea Righi <andrea.righi@canonical.com>
[esmil: handle linux-doc like the linux-source package]
Signed-off-by: Emil Renner Berthing <emil.renner.berthing@canonical.com>