stop the build break for btbridge on qemu

btbridge is not even part of the qemu image
diff --git a/meta-phosphor/conf/machine/include/sample.inc b/meta-phosphor/conf/machine/include/sample.inc
index 2b8f986..e71b85f 100644
--- a/meta-phosphor/conf/machine/include/sample.inc
+++ b/meta-phosphor/conf/machine/include/sample.inc
@@ -20,8 +20,7 @@
 VIRTUAL-RUNTIME_obmc-phosphor-ipmi-parsers = " \
         host-ipmid-oem \
        "
-
-PREFERRED_PROVIDER_virtual/obmc-phosphor-host-ipmi-hw ?= "host-ipmi-hw-example"
+PREFERRED_PROVIDER_virtual/obmc-phosphor-host-ipmi-hw = "host-ipmi-hw-example"
 PREFERRED_PROVIDER_virtual/obmc-phosphor-chassis-mgmt = "obmc-phosphor-chassisd"
 PREFERRED_PROVIDER_virtual/obmc-phosphor-event-mgmt = "obmc-phosphor-eventd"
 PREFERRED_PROVIDER_virtual/obmc-phosphor-fan-mgmt = "obmc-phosphor-fand"