Documentation: kvm: fix messy conversion from .txt to .rst

Building the documentation gives a warning that the KVM_PPC_RESIZE_HPT_PREPARE
label is defined twice.  The root cause is that the KVM_PPC_RESIZE_HPT_PREPARE
API is present twice, the second being a mix of the prepare and commit APIs.
Fix it.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>