Remove obmc-mrw machine feature

Using MRW or not is distro policy.  As such remove the obmc-mrw
machine feature.

Do not enable the remaining obmc-mrw distro feature in the base
phosphor distro configuration.

Create new distro configs for the systems that use MRW today
(i.e. Witherspoon) that enables the obmc-mrw distro feature and point
the local.conf.sample at the new distro configuration.

Change-Id: If4cedc745b3ee942518fbfd4d5cf2cd5b60f346d
Tested: Built a Witherspoon image and validate the manifest
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-witherspoon/conf/machine/witherspoon.conf b/meta-witherspoon/conf/machine/witherspoon.conf
index 806d534..0085a14 100644
--- a/meta-witherspoon/conf/machine/witherspoon.conf
+++ b/meta-witherspoon/conf/machine/witherspoon.conf
@@ -3,7 +3,7 @@
 
 UBOOT_MACHINE = "ast_g5_ncsi_config"
 
-OBMC_MACHINE_FEATURES += "obmc-mrw obmc-ubi-fs openpower-ubi-fs"
+OBMC_MACHINE_FEATURES += "obmc-ubi-fs openpower-ubi-fs"
 
 OBMC_POWER_SUPPLY_INSTANCES = "0 1"