Debian: enable OVN images for AArch64

Thomas Goirand uploaded OVN packages into official bullseye-backports
repository. They are available for both x86-64 and aarch64 so we can
enable them now.

Change-Id: I90abeca62e2de264539b711d8bea22ec17ff03c8

Author: hrw

doc/source/matrix_aarch64.csv

@@ -48,7 +48,7 @@ nova,C,C,C,C,N,C
 nova-spicehtml5proxy,N,N,C,C,N,C
 octavia,C,C,N,C,N,C
 openvswitch,C,C,C,C,N,C
-ovn,C,C,C,C,N,N
+ovn,C,C,C,C,C,C
 ovsdpdk,N,N,C,C,N,C
 placement,C,C,N,C,N,C
 prometheus,C,C,C,C,N,C

kolla/image/build.py

@@ -115,10 +115,6 @@ class Status(Enum):
         "qdrouterd",  # There is no qdrouterd package for Ubuntu
     },
 
-    'debian+aarch64': {
-        "ovn-base",      # no binary package
-    },
-
     'ubuntu+aarch64': {
         "kibana",        # no binary package
         "monasca-base",  # 'confluent-kafka' requires newer libfdkafka-dev