KVM: selftests: use X86_MEMTYPE_WB instead of VMX_BASIC_MEM_TYPE_WB

In 08a7d252 ("tools arch x86: Sync the msr-index.h copy with the
kernel sources"), VMX_BASIC_MEM_TYPE_WB was removed.  Use X86_MEMTYPE_WB
instead.

Fixes: 08a7d252 ("tools arch x86: Sync the msr-index.h copy with the
kernel sources")
Signed-off-by: John Sperbeck <jsperbeck@google.com>
Message-ID: <20241106034031.503291-1-jsperbeck@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>