video: driver: set clk_rate to zero before clk_disable

Video driver clk scaling is through mmrm. So without informing
to mmrm if we disable_clk, then mmrm will hold stale peak_current
values and that will lead to incorrect calculations at mmrm side.
So always request to set lowest clk corner to mmrm before calling
clk_disable_unprepare() api.

Change-Id: I3e54249430ec4e886afb42f5af6863c7e40686c4
Signed-off-by: Govindaraj Rajagopal <grajagop@codeaurora.org>

driver/vidc/src/venus_hfi.c

@@ -1560,6 +1560,8 @@ void __disable_unprepare_clks(struct msm_vidc_core *core)
 				__func__, cl->name);
 
 		clk_disable_unprepare(cl->clk);
+		if (cl->has_scaling)
+			__set_clk_rate(core, cl, 0);
 		cl->prev = 0;
 	}
 }
@@ -1647,6 +1649,8 @@ fail_clk_enable:
 		d_vpr_e("Clock: %s disable and unprepare\n",
 			cl->name);
 		clk_disable_unprepare(cl->clk);
+		if (cl->has_scaling)
+			__set_clk_rate(core, cl, 0);
 		cl->prev = 0;
 	}