DCE-KMD: Add helper macro to check non NULL

- This is a follow-up CL to address a comment in
  I885348a09eaac6e4362c89b59880fbd32d77d3b5

- This change will add a  helper macro, DCE_WARN_ON_NOT_NULL(x),
  to print a warning message if the input param is not NULL.
    - Added to dce.h

JIRA TDS-16126

Change-Id: I9b2c4ea89fa1682d18c20f68b14ab7696917f261
Signed-off-by: anupamg <anupamg@nvidia.com>
Reviewed-on: https://git-master.nvidia.com/r/c/linux-nv-oot/+/3251828
Reviewed-by: svcacv <svcacv@nvidia.com>
Reviewed-by: Arun Swain <arswain@nvidia.com>
GVS: buildbot_gerritrpt <buildbot_gerritrpt@nvidia.com>
Reviewed-by: Mahesh Kumar <mahkumar@nvidia.com>

drivers/platform/tegra/dce/include/dce.h

@@ -20,6 +20,13 @@
 #include <dce-client-ipc-internal.h>
 #include <dce-os-work.h>
 
+#define DCE_WARN_ON_NOT_NULL(x) \
+	do { \
+		if (x != NULL) { \
+			dce_os_warn(d, "Unexpected non-NULL value for " #x "\n"); \
+		} \
+	} while (0)
+
 #define DCE_MAX_CPU_IRQS 4
 
 /**