USB: add missing KERN_* constants to printks

According to kerneljanitors todo list all printk calls (beginning
a new line) should have an according KERN_* constant.
Those are the missing peaces here for the usb subsystem.

Signed-off-by: Frank Seidel <frank@f-seidel.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>