ibm: rainier: remove witherpsoon, ac-server overrides

Rainier mistakenly has witherspoon and ibm-ac-server machine overrides
applied.  Rainier is neither a witherspoon nor an ac-server (accelerated
compute); remove so overrides approrpriate to those system types are not
applied during a Rainier build.

(From meta-ibm rev: c8e0f7ce18f89b09265ed4d2019f8a15999624a7)

Change-Id: I3e931d032832bff0191eca2f4431e4bff1de2406
Signed-off-by: Brad Bishop <bradleyb@fuzziesquirrel.com>
diff --git a/meta-ibm/meta-witherspoon/conf/machine/rainier.conf b/meta-ibm/meta-witherspoon/conf/machine/rainier.conf
index 81d808a..03f2623 100644
--- a/meta-ibm/meta-witherspoon/conf/machine/rainier.conf
+++ b/meta-ibm/meta-witherspoon/conf/machine/rainier.conf
@@ -1,7 +1,6 @@
 KERNEL_DEVICETREE = "aspeed-bmc-ibm-rainier.dtb"
 UBOOT_MACHINE = "evb-ast2600_defconfig"
 
-MACHINEOVERRIDES =. "ibm-ac-server:witherspoon:"
 require conf/machine/include/ast2600.inc
 require conf/machine/include/obmc-bsp-common.inc
 require conf/machine/include/openpower.inc