nb/intel/snb: Drop NORTHBRIDGE_INTEL_IVYBRIDGE

We keep the support, though. Just now that `libgfxinit` is fixed, we
don't need the distinction anymore. Causally, we also don't need
CPU_INTEL_MODEL_306AX any more.

TEST=Played tint on kontron/ktqm77. Score 606

Change-Id: Id1e33c77f44a66baacba375cbb2aeb71effb7b76
Signed-off-by: Nico Huber <nico.huber@secunet.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/32737
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Arthur Heymans <arthur@aheymans.xyz>
diff --git a/src/cpu/intel/model_206ax/Kconfig b/src/cpu/intel/model_206ax/Kconfig
index f045e9a..dbb8982 100644
--- a/src/cpu/intel/model_206ax/Kconfig
+++ b/src/cpu/intel/model_206ax/Kconfig
@@ -1,10 +1,7 @@
 config CPU_INTEL_MODEL_206AX
 	bool
 
-config CPU_INTEL_MODEL_306AX
-	bool
-
-if CPU_INTEL_MODEL_206AX || CPU_INTEL_MODEL_306AX
+if CPU_INTEL_MODEL_206AX
 
 config CPU_SPECIFIC_OPTIONS
 	def_bool y