Bluetooth: iso: Compile conn.c for BT_ISO even without BT_CONN

If BT_ISO is enabled we now compile conn.c which contains a
lot of functionality used by BT_ISO, even for broadcast-iso
builds, i.e. builds that do not require BT_CONN.

Signed-off-by: Emil Gydesen <emil.gydesen@nordicsemi.no>

samples/bluetooth/iso_broadcast/prj.conf

@@ -5,4 +5,4 @@ CONFIG_BT_DEVICE_NAME="Test ISO Broadcaster"
 
 # Temporary, enable the following to meet BT_ISO dependencies
 CONFIG_BT_OBSERVER=y
-CONFIG_BT_PERIPHERAL=y
+CONFIG_BT_BROADCASTER=y

subsys/bluetooth/host/CMakeLists.txt

@@ -77,6 +77,7 @@ if(CONFIG_BT_HCI_HOST)
   zephyr_library_sources_ifdef(
     CONFIG_BT_ISO
     iso.c
+    conn.c
     )
 
   if(CONFIG_BT_DF)