I have now added the resume function at the the end of the hooks list in my /etc/mkinitcpio.conf.
After that I have launched sudo mkinitcpio -P and sudo update-grub as @Wollie recommended in this post.
Lauching sudo mkinitcpio -P, I can see the following warning message for each kernel:
-> Running build hook: [block]
==> WARNING: Possibly missing firmware for module: qed
==> WARNING: Possibly missing firmware for module: bfa
==> WARNING: Possibly missing firmware for module: qla2xxx
==> WARNING: Possibly missing firmware for module: qla1280
What does it exactly mean? Is there now a risk to restart or hibernate the computer?