update submodule and patches to QEMU 8.1.5

Most notable fixes from a Proxmox VE perspective are:

* "virtio-net: correctly copy vnet header when flushing TX"
  To prevent a stack overflow that could lead to leaking parts of the
  QEMU process's memory.
* "hw/pflash: implement update buffer for block writes"
  To prevent an edge case for half-completed writes. This potentially
  affected EFI disks.
* Fixes to i386 emulation and ARM emulation.

No changes for patches were necessary (all are just automatic context
changes).

Signed-off-by: Fiona Ebner <f.ebner@proxmox.com>

debian/patches/bitmap-mirror/0001-drive-mirror-add-support-for-sync-bitmap-mode-never.patch

@@ -360,7 +360,7 @@ index da5fb31089..32f0f9858a 100644
                    BlockdevOnError on_source_error,
                    BlockdevOnError on_target_error,
 diff --git a/qapi/block-core.json b/qapi/block-core.json
-index 2b1d493d6e..903392cb8f 100644
+index bca1a0c372..a5cea82139 100644
 --- a/qapi/block-core.json
 +++ b/qapi/block-core.json
 @@ -2145,6 +2145,15 @@