USB: debugfs: USB test mode support by usb debugfs

USB: debugfs: USB test mode support by usb debugfs

To generate USB testmode pattern by accessing usb debugfs. It
need to be enabled with enable "CONFIG_USB_DEBUG" in def_config.
And disable autosuspend by sysfs before test as below:
echo on > /sys/bus/usb/devices/.../power/control

Bug 1323709

Change-Id: I2c9d4cb304435e9d36f11a97a8db2d2ffd582ecf
Signed-off-by: Neil Chen <neilc@nvidia.com>
Reviewed-on: http://git-master/r/303705
Reviewed-by: Automatic_Commit_Validation_User
Reviewed-by: Suresh Mangipudi <smangipudi@nvidia.com>
GVS: Gerrit_Virtual_Submit
Reviewed-by: Venkat Moganty <vmoganty@nvidia.com>