boot/optee-os: use dedicated 3.13.0 patch directory

Existing patch is for 3.13.0 optee version but is located at the root
of optee-os folder, leading to error when applying it on more recent
version. Move it to a dedicated 3.13.0 folder.

Signed-off-by: Clément Léger <clement.leger@bootlin.com>
Signed-off-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>