staging: wilc1000: use netdev_err instead of PRINT_ER

This patch uses netdev_err instead of PRINT_ER that is a custom debug
print.

Signed-off-by: Chaehyun Lim <chaehyun.lim@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>