USB: do not print -ESHUTDOWN message if usb at otg device mode

At otg device mode, the otg host resume should do no-op during
system resume, otherwise, the otg device will be treated as a
host for enumeration.

So, the otg host driver returns -ESHUTDOWN if it detects the
current usb mode is device mode. The host driver has to return
-ESHUTDOWN, otherwise, the usb_hc_died will be called.

Signed-off-by: Peter Chen <peter.chen@freescale.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>