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>

src/arch/x86/car.ld

@@ -91,9 +91,7 @@
 	_car_global_end = .;
 	_car_relocatable_data_end = .;
 
-#if (CONFIG(NORTHBRIDGE_INTEL_SANDYBRIDGE) || \
-    CONFIG(NORTHBRIDGE_INTEL_IVYBRIDGE)) && \
-    !CONFIG(USE_NATIVE_RAMINIT)
+#if CONFIG(NORTHBRIDGE_INTEL_SANDYBRIDGE) && !CONFIG(USE_NATIVE_RAMINIT)
 	. = ABSOLUTE(0xff7e1000);
 	_mrc_pool = .;
 	. += 0x5000;