meta-ibm: witherspoon: Set QB_DEFAULT_FSTYPE for use of UBI

Witherspoon uses UBI instead of static partitioning for flash
management, so make sure the qemu helper script can find the flash
image.

Tested: Reached a login prompt with `runqemu nographic slirp`.

Change-Id: I513d0a5b878c553456d70bef25adedfa25bf9c90
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/meta-ibm/conf/machine/witherspoon.conf b/meta-ibm/conf/machine/witherspoon.conf
index b1d9ca2..9b8e3f1 100644
--- a/meta-ibm/conf/machine/witherspoon.conf
+++ b/meta-ibm/conf/machine/witherspoon.conf
@@ -38,5 +38,6 @@
 
 IMAGE_FEATURES:remove = "obmc-ikvm"
 
+QB_DEFAULT_FSTYPE:witherspoon = "ubi.mtd"
 QB_MACHINE:witherspoon = "-machine witherspoon-bmc"
 QB_MEM:witherspoon = "-m 512"