Staging: comedi: fix build errors

Some of the comedi drivers need timer.h to build properly, so put it
in the comedidev.h file to fix these errors.
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/comedi/comedidev.h

@@ -39,6 +39,7 @@
 #include <linux/dma-mapping.h>
 #include <linux/uaccess.h>
 #include <linux/io.h>
+#include <linux/timer.h>
 
 #include "comedi.h"