USB: debugfs: USB test mode support with usb debugfs

To generate USB testmode pattern by accessing usb debugfs. It
need to be enabled with enable "CONFIG_USB_DEBUG" and disable
"CONFIG_USB_SUSPEND" config in def_config.

Bug 1323709

Change-Id: I2c9d4cb304435e9d36f11a97a8db2d2ffd582ecf
Signed-off-by: Neil Chen <neilc@nvidia.com>
Reviewed-on: http://git-master/r/250068
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Suresh Mangipudi <smangipudi@nvidia.com>
Reviewed-by: Petlozu Pravareshwar <petlozup@nvidia.com>
Reviewed-by: Venkat Moganty <vmoganty@nvidia.com>