KVM: x86: hyper-v: replace bitmap_weight() with hweight64()

KVM: x86: hyper-v: replace bitmap_weight() with hweight64()

kvm_hv_flush_tlb() applies bitmap API to a u64 variable valid_bank_mask.
Since valid_bank_mask has a fixed size, we can use hweight64() and avoid
excessive bloating.

CC: Borislav Petkov <bp@alien8.de>
CC: Dave Hansen <dave.hansen@linux.intel.com>
CC: H. Peter Anvin <hpa@zytor.com>
CC: Ingo Molnar <mingo@redhat.com>
CC: Jim Mattson <jmattson@google.com>
CC: Joerg Roedel <joro@8bytes.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Sean Christopherson <seanjc@google.com>
CC: Thomas Gleixner <tglx@linutronix.de>
CC: Vitaly Kuznetsov <vkuznets@redhat.com>
CC: Wanpeng Li <wanpengli@tencent.com>
CC: kvm@vger.kernel.org
CC: linux-kernel@vger.kernel.org
CC: x86@kernel.org
Acked-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Yury Norov <yury.norov@gmail.com>