Staging: rtl8188eu: Fix warning of printk() should include KERN_ facility level.

This patch fixes the warning of "printk() should include KERN_ facility
level" in file rtw_debug.c.

Signed-off-by: Elena Oat <oat.elena@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>