Fix WHPX issue leaking tpr values

Fix WHPX issue leaking tpr values

Fixes an issue where if the tpr is assigned to the array but not a different
value from what is already expected on the vp the code will skip incrementing
the reg_count. In this case its possible that we set an invalid memory section
of the next call for DeliverabilityNotifications that was not expected.

The fix is to use a local variable to store the temporary tpr and only update
the array if the local tpr value is different than the vp context.

Signed-off-by: Justin Terry (VM) <juterry@microsoft.com>
Message-Id: <1519665216-1078-7-git-send-email-juterry@microsoft.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Justin Terry (VM) via Qemu-devel <qemu-devel@nongnu.org>