spl: update submodule to debian/0.7.12-1

Reviewed-by: Stoiko Ivanov <s.ivanov@proxmox.com>
Tested-by: Stoiko Ivanov <s.ivanov@proxmox.com>
Signed-off-by: Fabian Grünbichler <f.gruenbichler@proxmox.com>

diff --git a/spl-debian b/spl-debian
index 3ac1211d59ab3a6d124fb67a8cea987a66099781..64ef8d91c0818fcddbedf441d0d005712b8954e5 160000 (submodule)
--- a/spl-debian
+++ b/spl-debian
@@ -1 +1 @@
-Subproject commit 3ac1211d59ab3a6d124fb67a8cea987a66099781
+Subproject commit 64ef8d91c0818fcddbedf441d0d005712b8954e5