USB: usbatm: remove unneeded trace printk calls

We have an in-kernel trace subsystem, so use that instead of printk for
trying to figure out what functions are being called.

Cc: Duncan Sands <duncan.sands@free.fr>
Acked-by: Felipe Balbi <balbi@ti.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>