staging: ozwpan: Make oz_hcd_pd_arrived() return a struct pointer

oz_hcd_pd_arrived returns struct oz_port *, change function
declaration to avoid ambiguity.

Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Rupesh Gujare <rupesh.gujare@atmel.com>
Reviewed-by: Dan Carpenter <dan.carpenter@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>