KVM: x86: bit-ops emulation ignores offset on 64-bit

The current emulation of bit operations ignores the offset from the destination
on 64-bit target memory operands. This patch fixes this behavior.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>