update kernel to 5.11.21 with Ubuntu-5.11.0-19.20

Signed-off-by: Thomas Lamprecht <t.lamprecht@proxmox.com>

diff --git a/submodules/ubuntu-hirsute b/submodules/ubuntu-hirsute
index 8c0148239f4cd0bda2bca10770e9bf4ef284b4d2..6c982603b0dffdfff74e4faccb4388d64719530b 160000 (submodule)
--- a/submodules/ubuntu-hirsute
+++ b/submodules/ubuntu-hirsute
@@ -1 +1 @@
-Subproject commit 8c0148239f4cd0bda2bca10770e9bf4ef284b4d2
+Subproject commit 6c982603b0dffdfff74e4faccb4388d64719530b