Using multiple calls to error_report here means every line is
prefaced with the (potentially long) pci-assign command line
arguments.

Use a single error_printf to preserve the intended formatting.
Since this code path is always preceded by an error_report call,
we don't lose the command line reporting.
Signed-off-by: NCole Robinson <crobinso@redhat.com>
Reviewed-by: NMarkus Armbruster <armbru@redhat.com>
Signed-off-by: NMichael Tokarev <mjt@tls.msk.ru>