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-ibm/conf/machine/p10bmc.conf b/meta-ibm/conf/machine/p10bmc.conf
index 1891129..b714f78 100644
--- a/meta-ibm/conf/machine/p10bmc.conf
+++ b/meta-ibm/conf/machine/p10bmc.conf
@@ -15,7 +15,7 @@
 require conf/distro/include/ibm-mpreboot.inc
 require conf/distro/include/ibm-yaml.inc
 DISTRO_FEATURES += "ibm-service-account-policy"
-OBMC_MACHINE_FEATURES += 'phal'
+MACHINE_FEATURES += 'phal'
 
 SERIAL_CONSOLES = "115200;ttyS4"