KVM: x86: limit PIT timer frequency

Limit PIT timer frequency similarly to the limit applied by
LAPIC timer.

Cc: stable@kernel.org
Reviewed-by: Jan Kiszka <jan.kiszka@siemens.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --cc arch/x86/kvm/i8254.c
Simple merge

diff --cc arch/x86/kvm/lapic.c
Simple merge

diff --cc arch/x86/kvm/x86.c
Simple merge

diff --cc arch/x86/kvm/x86.h
Simple merge