usb: ulpi: remove "dev" field from struct ulpi_ops

Operations now use ulpi->dev.parent directly instead of via the
ulpi_ops struct, making this field unused. Remove it.

Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: Tal Shorer <tal.shorer@gmail.com>
Signed-off-by: Felipe Balbi <felipe.balbi@linux.intel.com>