x86/kvm: remove unused macro HV_CLOCK_SIZE

This macro is useless, and could cause gcc warning:
arch/x86/kernel/kvmclock.c:47:0: warning: macro "HV_CLOCK_SIZE" is not
used [-Wunused-macros]
Let's remove it.

Signed-off-by: Alex Shi <alex.shi@linux.alibaba.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Sean Christopherson <sean.j.christopherson@intel.com>
Cc: Vitaly Kuznetsov <vkuznets@redhat.com>
Cc: Wanpeng Li <wanpengli@tencent.com>
Cc: Jim Mattson <jmattson@google.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Borislav Petkov <bp@alien8.de>
Cc: x86@kernel.org
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Message-Id: <1604651963-10067-1-git-send-email-alex.shi@linux.alibaba.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>