UPSTREAM: ath10k: add hif power-up/power-down methods

Add hif power-up/power-down methods for wcn3990
target.

Signed-off-by: Govind Singh <govinds@codeaurora.org>
Signed-off-by: Kalle Valo <kvalo@codeaurora.org>
Git-commit: 0fa4fbe9b8cf7656813382602a6a5d330f01d3ae
Git-repo: git://git.kernel.org/pub/scm/linux/kernel/git/kvalo/ath.git


Change-Id: I36434fd36486ed07de3d121b49bd142a1a50256f
Signed-off-by: Dundi Raviteja <dundi@codeaurora.org>