[media] V4L: mem2mem: fix alignment in mem2mem-testdev

Fix a trivial alignment calculation issue.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@gmx.de>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/mem2mem_testdev.c

@@ -40,7 +40,7 @@ MODULE_VERSION("0.1.1");
 #define MIN_H 32
 #define MAX_W 640
 #define MAX_H 480
-#define DIM_ALIGN_MASK 0x08 /* 8-alignment for dimensions */
+#define DIM_ALIGN_MASK 7 /* 8-byte alignment for line length */
 
 /* Flags that indicate a format can be used for capture/output */
 #define MEM2MEM_CAPTURE	(1 << 0)