KVM: x86/mmu: Fix uninitialized boolean variable flush

In the case where kvm_memslots_have_rmaps(kvm) is false the boolean
variable flush is not set and is uninitialized.  If is_tdp_mmu_enabled(kvm)
is true then the call to kvm_tdp_mmu_zap_collapsible_sptes passes the
uninitialized value of flush into the call. Fix this by initializing
flush to false.

Addresses-Coverity: ("Uninitialized scalar variable")
Fixes: e2209710

 ("KVM: x86/mmu: Skip rmap operations if rmaps not allocated")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Reviewed-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210622150912.23429-1-colin.king@canonical.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>