Revert "Remove code that enables/disables VMX in coreboot on chromebooks."

The MSR for VMX can start with a random value and needs to be
cleared by coreboot. I am reverting this change, as
it handles almost everything and doing a follow-on change to fix
the improper clearing of the MSR.

Change-Id: Ibad7a27b03f199241c52c1ebdd2b6d4e81a18a4e
Signed-off-by: Marc Jones <marc.jones@se-eng.com>
Reviewed-on: http://review.coreboot.org/1793
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

src/cpu/intel/model_206ax/Kconfig

@@ -28,6 +28,10 @@ config SMM_TSEG_SIZE
 	hex
 	default 0x800000
 
+config ENABLE_VMX
+	bool "Enable VMX for virtualization"
+	default n
+
 config MICROCODE_INCLUDE_PATH
 	string
 	default "src/cpu/intel/model_206ax"