staging: wlan-ng: prism2usb.c: fix printk(KERN_ERR... to dev_err(dev, ...

Fix checkpatch warning. Change printk(KERN_ERR ... to dev_err(dev ...

Signed-off-by: Nick Østergaard <oe.nick@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>