openssl: use git formatted patches

Using Git formatted patches makes it easier to adjust the patches when
needed.

[Thomas: remove patch numbering.]

Signed-off-by: Ryan Barnett <ryanbarnett3@gmail.com>
CC: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
CC: Gustavo Zacarias <gustavo@zacarias.com.ar>
CC: Arnout Vandecappelle <arnout@mind.be>
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>