libvfio-user: update for MD5_*() deprecation

Compilation with newer openssl fails, as MD5_*() API is now marked
deprecated. Update submodule to fix this.

Fixes #2459
Signed-off-by: John Levon <john.levon@nutanix.com>
Change-Id: I64f5e1946a956ed5252e4f4213399ee2808a2e2a
Reviewed-on: https://review.spdk.io/gerrit/c/spdk/spdk/+/12639


Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
Community-CI: Mellanox Build Bot
Community-CI: Broadcom CI <spdk-ci.pdl@broadcom.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Reviewed-by: Changpeng Liu <changpeng.liu@intel.com>