Convert obmc-ubi-fs to a distro feature

As with MRW the use of the UBI image scheme is distro policy.
Convert the existing machine feature to a distro feature.

Enable the new distro feature on the systems that use
it(Witherspoon).

Add a distro override and fix-up MF checks to use this override
instead for improved readability.

Tested: Built a Witherspoon image and validated image
Change-Id: I8ab03115bbfc2ecc77cff5c9eb8628903ae88051
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-phosphor/conf/machine/include/obmc-bsp-common.inc b/meta-phosphor/conf/machine/include/obmc-bsp-common.inc
index 165eca4..2cbdd89 100644
--- a/meta-phosphor/conf/machine/include/obmc-bsp-common.inc
+++ b/meta-phosphor/conf/machine/include/obmc-bsp-common.inc
@@ -11,7 +11,7 @@
 MACHINEOVERRIDES =. "openbmc:"
 
 IMAGE_FSTYPES += "cpio.${INITRAMFS_CTYPE}.u-boot"
-IMAGE_FSTYPES += "${@bb.utils.contains('MACHINE_FEATURES', \
+IMAGE_FSTYPES += "${@bb.utils.contains('DISTRO_FEATURES', \
         'obmc-ubi-fs', \
         'mtd-ubi mtd-ubi-tar', \
         'mtd-static mtd-static-tar mtd-static-alltar', d)}"
@@ -19,8 +19,8 @@
 
 INITRAMFS_CTYPE ?= "lzma"
 INITRAMFS_FSTYPES += "cpio.${INITRAMFS_CTYPE}"
-INITRAMFS_IMAGE = "${@bb.utils.contains('MACHINE_FEATURES', \
-        'obmc-ubi-fs', '', 'obmc-phosphor-initramfs', d)}"
+INITRAMFS_IMAGE ?= "obmc-phosphor-initramfs"
+INITRAMFS_IMAGE_df-obmc-ubi-fs ?= ""
 
 MACHINE_FEATURES_BACKFILL_CONSIDERED = "qemu-usermode"