tegra usb: Switching of USB busy hints, when no active USB tranfers

tegra usb: Switching of USB busy hints, when no active USB tranfers
           are happening though a device connection on host port.

Currently for harmony, an intergrated SMSC hub present on USB3. Because
of this device connection is present on USB3 and USB power busy hints
are always on. To avoid this, for host by default busy hints are off and
USB busy hints will be on for :
1.Bulk and isochronus transfers
2.Interrupts transfers with buffer length >= 256.
Busy hint will be on for pre-defined amount of time
and after that busy hints will be off automatically.

With this in idle state power is reduced.

Tested on : Harmony
Enumeartion is happening fine.
LAN and USB HID devices are working fine

Change-Id: Ifd653bebfb52c7702f7d24bf11ccf93e62ea0f66
Reviewed-on: http://git-master/r/915
Reviewed-by: Gary King <gking@nvidia.com>
Tested-by: Gary King <gking@nvidia.com>