Incorrect checkout of git submodules

Incorrect checkout of git submodules

When checking out git packages, buildroot doesn't seem to track the revisions
correctly of any submodules referenced by that project. As a result, the
submodule stays at whatever revision was referenced by the head of the master
branch. Running a 'git submodule update' after the checkout fixes this problem.

Signed-off-by: Owen Kirby <osk@exegin.com>
git-svn-id: svn://svn.openwrt.org/openwrt/trunk@38359 3c298f89-4303-0410-b956-a3cf2f4a3e73