meta-ibm: witherspoon-tacoma: Disable socsec signing

Don't support the hardware root-of-trust on Tacoma boards.

Change-Id: I144d3bf445063f6341ae1958611873f79c9c00c7
Signed-off-by: Andrew Jeffery <andrew@aj.id.au>
diff --git a/meta-ibm/conf/machine/witherspoon-tacoma.conf b/meta-ibm/conf/machine/witherspoon-tacoma.conf
index 5e10dc3..e273726 100644
--- a/meta-ibm/conf/machine/witherspoon-tacoma.conf
+++ b/meta-ibm/conf/machine/witherspoon-tacoma.conf
@@ -2,6 +2,7 @@
 UBOOT_MACHINE = "ast2600_openbmc_spl_emmc_defconfig"
 UBOOT_DEVICETREE = "ast2600-tacoma"
 SPL_BINARY = "spl/u-boot-spl.bin"
+SOCSEC_SIGN_ENABLE = "0"
 
 OBMC_POWER_SUPPLY_INSTANCES = "0 1"