staging: vchiq_2835_arm: Make cache-line-size a required DT property

The original github source allowed for the cache-line-size property
to be missing.  Since recent firmwares also require this property,
it makes sense to always require it in the driver as well.

If the cache-line-size property is missing, then the driver probe
should fail as no dev since the kernel and dt may be out of sync.
The fix is to add a check for the return value of of_property_read_u32.

Changes V2:
	1. Add error message if cache-line-size is missing.
	2. Simple check for non-zero return value from
	   of_property_read_u32.
Signed-off-by: Michael Zoran <mzoran@crowfest.net>
Acked-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/staging/vc04_services/interface/vchiq_arm/vchiq_2835_arm.c

@@ -121,8 +121,14 @@ int vchiq_platform_init(struct platform_device *pdev, VCHIQ_STATE_T *state)
 	if (err < 0)
 		return err;
 
-	(void)of_property_read_u32(dev->of_node, "cache-line-size",
+	err = of_property_read_u32(dev->of_node, "cache-line-size",
 				   &g_cache_line_size);
+
+	if (err) {
+		dev_err(dev, "Missing cache-line-size property\n");
+		return -ENODEV;
+	}
+
 	g_fragments_size = 2 * g_cache_line_size;
 
 	/* Allocate space for the channels in coherent memory */