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-openpower/conf/machine/include/p9.inc b/meta-openpower/conf/machine/include/p9.inc
index 2da9fd1..5c17793 100644
--- a/meta-openpower/conf/machine/include/p9.inc
+++ b/meta-openpower/conf/machine/include/p9.inc
@@ -1,3 +1,3 @@
 include conf/machine/include/ibm-power9-cpu.inc
-OBMC_MACHINE_FEATURES += 'op-fsi p9-cfam-override'
+MACHINE_FEATURES += 'op-fsi p9-cfam-override'
 PREFERRED_PROVIDER_virtual/obmc-host-ctl = "p9-host-start"