i386/kvm/pci-assign: Use errp directly rather than local_err

i386/kvm/pci-assign: Use errp directly rather than local_err

In assigned_device_pci_cap_init(), first, error messages are filled
to a local_err variable, then through error_propagate() pass to
the parameter of errp. It leads to cumbersome code. In order to
avoid the extra local_err and error_propagate(), drop it and use
errp instead.

Cc: pbonzini@redhat.com
Cc: rth@twiddle.net
Cc: ehabkost@redhat.com
Cc: mst@redhat.com
Cc: armbru@redhat.com
Cc: marcel@redhat.com
Signed-off-by: Mao Zhongyi <maozy.fnst@cn.fujitsu.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>