Staging: hp: Use netdev_warn().

This replaces printk(KERN_WARNING ..) with netdev_warn(),
as the use of printk() isn't preferred when
a struct net_device is available.

Signed-off-by: Sam Muhammed <jane.pnx9@gmail.com>
Acked-by: Julia Lawall <julia.lawall@inria.fr>
Link: https://lore.kernel.org/r/20200322115051.2767-1-jane.pnx9@gmail.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>