Revert "drm: Use a flexible array member for blob property data"

Using a flexible array for the blob data was a mistake by me. It
forces all users of the blob data to cast blob->data to something
else. void* is clearly superior so let's go back to the original
scheme.

Not a clean revert as the code has moved.

This reverts commit d63f5e6bf6f2a1573ea39c9937cdf5ab0b3a4b77.

Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180223192506.29992-1-ville.syrjala@linux.intel.com
Reviewed-by: Shashank Sharma <shashank.sharma@intel.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_property.c

@@ -567,6 +567,7 @@ drm_property_create_blob(struct drm_device *dev, size_t length,
 	/* This must be explicitly initialised, so we can safely call list_del
 	 * on it in the removal handler, even if it isn't in a file list. */
 	INIT_LIST_HEAD(&blob->head_file);
+	blob->data = (void *)blob + sizeof(*blob);
 	blob->length = length;
 	blob->dev = dev;
 

include/drm/drm_property.h

@@ -209,7 +209,7 @@ struct drm_property_blob {
 	struct list_head head_global;
 	struct list_head head_file;
 	size_t length;
-	unsigned char data[];
+	void *data;
 };
 
 struct drm_prop_enum_list {