hardening: x86: drop reference to removed config AMD_IOMMU_V2

Commit 5a0b11a1 ("iommu/amd: Remove iommu_v2 module") removes the
config AMD_IOMMU_V2.

Remove the reference to this config in the x86 architecture-specific
hardening config fragment as well.
Signed-off-by: Lukas Bulwahn <lukas.bulwahn@gmail.com>
Reviewed-by: Vasant Hegde <vasant.hegde@amd.com>
Link: https://lore.kernel.org/r/20231012045040.22088-1-lukas.bulwahn@gmail.comSigned-off-by: Kees Cook <keescook@chromium.org>

arch/x86/configs/hardening.config

@@ -9,7 +9,6 @@ CONFIG_INTEL_IOMMU=y
 CONFIG_INTEL_IOMMU_DEFAULT_ON=y
 CONFIG_INTEL_IOMMU_SVM=y
 CONFIG_AMD_IOMMU=y
-CONFIG_AMD_IOMMU_V2=y
 
 # Enable CET Shadow Stack for userspace.
 CONFIG_X86_USER_SHADOW_STACK=y