For systems using the Mentor HDRC controllers we get better TX DMA throughput
if we can avoid falling back to PIO to write zero length packets ... so tell
the driver to avoid ZLPs.
Signed-off-by: NDavid Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: NGreg Kroah-Hartman <gregkh@suse.de>