KVM: x86: Clean up redundant ROL16(val, n) macro definition

The ROL16(val, n) macro is repeatedly defined in several vmcs-related
files, and it has never been used outside the KVM context.

Let's move it to vmcs.h without any intended functional changes.

Signed-off-by: Like Xu <likexu@tencent.com>
Message-Id: <20210809093410.59304-4-likexu@tencent.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>