git packages: use full revision hash

There is no benefit in using the shortened git revision hash. On the
contrary: the shorter the hash, the higher the risk of having collisions
with another commit.

Signed-off-by: Thomas De Schampheleire <thomas.de.schampheleire@gmail.com>
Acked-by: Samuel Martin <s.martin49@gmail.com>
Acked-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>