power: avs: qcom-cpr: make cpr_get_opp_hz_for_req() static

drivers/power/avs/qcom-cpr.c:1081:15:
warning: no previous prototype for ‘cpr_get_opp_hz_for_req’

Detected when running make with W=1.
Signed-off-by: Niklas Cassel <nks@flawful.org>
Reviewed-by: Bjorn Andersson <bjorn.andersson@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

drivers/power/avs/qcom-cpr.c

@@ -1078,8 +1078,8 @@ static unsigned int cpr_get_fuse_corner(struct dev_pm_opp *opp)
 	return fuse_corner;
 }
 
-unsigned long cpr_get_opp_hz_for_req(struct dev_pm_opp *ref,
-				     struct device *cpu_dev)
+static unsigned long cpr_get_opp_hz_for_req(struct dev_pm_opp *ref,
+					    struct device *cpu_dev)
 {
 	u64 rate = 0;
 	struct device_node *ref_np;