Makefile: Add `make upgrade` target

Makefile: Add `make upgrade` target

1. Fix missing default `make` target for `all`

2. `make submodules-clean` should checkout git submodule commit

   On patch apply, we tag the starting commit, so we can later export
   as patches all commits between that reference and another tag,
   applied simmetrically at the  end of the patch apply process.
   Previously, `submodules-clean` checked out that starting tag.
   Change that behavior to use the commit ID referenced by parent
   git repo (armband) submodule, so when armband git submodules are
   updated (e.g. sometimes `make upgrade` might include such changes),
   the new reference will be picked up automatically.

3. Add `make upgrade` for fetching latest changes on current branch

Change-Id: I03dc3953e91acfbe6ccb5e3bb2ccee7d28a0f7d5
Signed-off-by: Alexandru Avadanii <Alexandru.Avadanii@enea.com>