arm64:tegre:loki: Enable LEDs as a USB device

arm64:tegre:loki: Enable LEDs as a USB device

This change enables the USB driver for the LEDs on
the Loki touch button board. The driver creates sysfs
nodes that would allow a userspace service to alter
the state and brightness of the LEDs.

Bug 1550625

Change-Id: I147c4530278774bfdda486b01ce7e8aa28a7dbd3
Signed-off-by: Ankita Garg <ankitag@nvidia.com>
Reviewed-on: http://git-master/r/496965
Reviewed-by: Automatic_Commit_Validation_User
GVS: Gerrit_Virtual_Submit
Reviewed-by: Raymond Poudrier <rapoudrier@nvidia.com>