drivers: net: rmnet: Power collapse feature

Enable power collapse in rmnet driver. Rmnet
driver is not able to go into power collapse
unless dl marker/fc indications stop.
Deregistration of these indications should
take place when there is no longer any more
rmnet traffic. This change allows for dereg
of these indications with use of periodic wq.

CRs-Fixed: 2277101
Change-Id: I6a95307f5988279507e0b0b35559d7872d693c71
Acked-by: Raul Martinez <mraul@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>