msm: ipa3: USB DPL channel suspend/resume support

This support will allow USB driver to initiate suspend/resume
requests to IPA driver for the DPL channel.
IPA driver should allow suspend/resume of the DPL channel
regardless of the state of the data tethering channels.

Change-Id: I47a0963be8a7a08425ae7bfa6c78755f9f528206
Signed-off-by: Ghanim Fodi <gfodi@codeaurora.org>