treewide: clean up use of OBMC_MACHINE_FEATURES

Modify the machine meta-layer configs to remove the use of the
OBMC_MACHINE_FEATURES indirection and favor the Yocto MACHINE_FEATURES
variable instead.

Signed-off-by: Patrick Williams <patrick@stwcx.xyz>
Change-Id: Ifafb79e4e4c010e9476b9547cd4982f5b645060e
diff --git a/meta-facebook/conf/machine/include/facebook-withhost.inc b/meta-facebook/conf/machine/include/facebook-withhost.inc
index ebe79d1..8567f69 100644
--- a/meta-facebook/conf/machine/include/facebook-withhost.inc
+++ b/meta-facebook/conf/machine/include/facebook-withhost.inc
@@ -1,6 +1,6 @@
 require conf/machine/include/facebook.inc
 
-OBMC_MACHINE_FEATURES += "\
+MACHINE_FEATURES += "\
         obmc-chassis-state-mgmt \
         obmc-host-ipmi \
         obmc-host-state-mgmt \