Staging: slicoss: Replace printk() with pr_debug() or dev_dbg() as required

This patch fixes the following checkpatch.pl warning in slicoss.c:
WARNING: Prefer netdev_dbg(netdev, ... then dev_dbg(dev, ... then
pr_debug(...  to printk(KERN_DEBUG ...

Signed-off-by: Rashika Kheria <rashika.kheria@gmail.com>
Reviewed-by: Peter P Waskiewicz Jr <peter.p.waskiewicz.jr@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>