hw/9pfs: Remove virtio-9p-debug.* infra to be replaced by Qemu Tracing.

Removing the existing debug infrastrucure as proposed to be replaced by
Qemu Tracing infrastructure.

Reviewed-by: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Harsh Prateek Bora <harsh@linux.vnet.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>