soc: qcom: wda: Power Save cb support

Added Power save mode indication registration.
Modules should be able to be notified when rmnet is
going into ps mode.

CRs-Fixed: 2316002
Change-Id: I0b11e4aa6595d51b7421e3cc0acbab4bf13dd18a
Acked-by: Raul Martinez <mraul@qti.qualcomm.com>
Signed-off-by: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>