staging: unisys: virtpci: virtpci.c: Removes unnecessary NULL check

It is impossible for dprivate to ever be NULL, no check required.

Signed-off-by: Rickard Strandqvist <rickard_strandqvist@spectrumdigital.se>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>