Setup instructions don't match the code anymore, ever since the split
to a separate repo we don't set it up automatically anymore. Readd
that - the right link and all was already there.

v2: 100% fewer typos (hopefully)

Reported-by: Dave Airlie <airlied@gmail.com>
Cc: Dave Airlie <airlied@gmail.com>
Acked-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>