target-i386: reorder fields in cpu/msr_hyperv_hypercall subsection

The subsection already exists in one well-known enterprise Linux
distribution, but for some strange reason the fields were swapped
when forward-porting the patch to upstream.

Limit headaches for said enterprise Linux distributor when the
time will come to rebase their version of QEMU.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1396452782-21473-1-git-send-email-pbonzini@redhat.com
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
