dwc3: Add USB function suspend/resume related handling

Currently dwc3 driver doesn't hand over USB function suspend/resume
request to composite layer as those are supposed to be handle by
USB function driver. This change adds support for it. It also adds
function remote wakeup functionality which is needed by USB function
suspended interface to perform remote wakeup towards USB host for
resume interface related functionality.

Change-Id: I1f9ecc60346e16fad87439cc12c551e05b4f3491
Signed-off-by: Mayank Rana <mrana@codeaurora.org>