V4L/DVB: vivi and mem2mem_testdev need slab.h to build

Fix vivi and mem2mem_testdev build errors: need to #include <linux/slab.h>:

drivers/media/video/vivi.c:1144: error: implicit declaration of function 'kfree'
drivers/media/video/vivi.c:1156: error: implicit declaration of function 'kzalloc'
drivers/media/video/vivi.c:1156: warning: assignment makes pointer from integer without a cast
drivers/media/video/mem2mem_testdev.c:862: error: implicit declaration of function 'kzalloc'
drivers/media/video/mem2mem_testdev.c:862: warning: assignment makes pointer from integer without a cast
drivers/media/video/mem2mem_testdev.c:874: error: implicit declaration of function 'kfree'
drivers/media/video/mem2mem_testdev.c:944: warning: assignment makes pointer from integer without a cast

Signed-off-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

drivers/media/video/mem2mem_testdev.c

@@ -22,6 +22,7 @@
 #include <linux/version.h>
 #include <linux/timer.h>
 #include <linux/sched.h>
+#include <linux/slab.h>
 
 #include <linux/platform_device.h>
 #include <media/v4l2-mem2mem.h>

drivers/media/video/vivi.c

@@ -17,6 +17,7 @@
 #include <linux/kernel.h>
 #include <linux/init.h>
 #include <linux/sched.h>
+#include <linux/slab.h>
 #include <linux/font.h>
 #include <linux/version.h>
 #include <linux/mutex.h>