mailbox: qcom-apcs-ipc: enable APCS clock device for MSM8996

MSM8996 also has the clock-related part of the APCS mailbox device.
Follow the usual pattern and create a child device to handle these
clocks.

Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Signed-off-by: Jassi Brar <jaswinder.singh@linaro.org>

drivers/mailbox/qcom-apcs-ipc-mailbox.c

@@ -42,7 +42,7 @@ static const struct qcom_apcs_ipc_data msm8994_apcs_data = {
 };
 
 static const struct qcom_apcs_ipc_data msm8996_apcs_data = {
-	.offset = 16, .clk_name = NULL
+	.offset = 16, .clk_name = "qcom-apcs-msm8996-clk"
 };
 
 static const struct qcom_apcs_ipc_data apps_shared_apcs_data = {