msm: kgsl: Reimplement the timestamp comparison function

Make timestamp_cmp return -1, 0 or 1 depending if
the first operand is less than, equal or greater
than the second operand.

Change-Id: Ic0dedbad0ea2d918e0eeef9428859f0b54a6e7ad
Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
diff --git a/drivers/gpu/msm/z180.c b/drivers/gpu/msm/z180.c
index 9e14247..cdb9c23 100644
--- a/drivers/gpu/msm/z180.c
+++ b/drivers/gpu/msm/z180.c
@@ -378,7 +378,8 @@
 	int status = 0;
 	struct z180_device *z180_dev = Z180_DEVICE(device);
 
-	if (z180_dev->current_timestamp > z180_dev->timestamp)
+	if (timestamp_cmp(z180_dev->current_timestamp,
+		z180_dev->timestamp) > 0)
 		status = z180_wait(device, z180_dev->current_timestamp,
 					timeout);
 
@@ -644,15 +645,10 @@
 
 static unsigned int z180_isidle(struct kgsl_device *device)
 {
-	int status = false;
 	struct z180_device *z180_dev = Z180_DEVICE(device);
 
-	int timestamp = z180_dev->timestamp;
-
-	if (timestamp == z180_dev->current_timestamp)
-		status = true;
-
-	return status;
+	return (timestamp_cmp(z180_dev->timestamp,
+		z180_dev->current_timestamp) == 0) ? true : false;
 }
 
 static int z180_suspend_context(struct kgsl_device *device)