meta-facebook: more prep for new override syntax

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: I21120d6215c25be49afd60d6e807b68f2798423a
diff --git a/meta-facebook/meta-yosemitev2/conf/machine/yosemitev2.conf b/meta-facebook/meta-yosemitev2/conf/machine/yosemitev2.conf
index 9119189..d246cc9 100644
--- a/meta-facebook/meta-yosemitev2/conf/machine/yosemitev2.conf
+++ b/meta-facebook/meta-yosemitev2/conf/machine/yosemitev2.conf
@@ -9,6 +9,6 @@
 
 SERIAL_CONSOLES = "57600;ttyS4"
 
-PREFERRED_PROVIDER:virtual/obmc-host-ctl ?= ""
+PREFERRED_PROVIDER_virtual/obmc-host-ctl ?= ""
 FLASH_SIZE = "32768"
 OBMC_HOST_INSTANCES = "1 2 3 4"