Input: pegasus_notetaker - directly include workqueue header

According to the kernel's guidelines, let's directly include the
workqueue functions we use.
Signed-off-by: Martin Kepplinger <martink@posteo.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/tablet/pegasus_notetaker.c

@@ -40,6 +40,7 @@
 #include <linux/input.h>
 #include <linux/usb/input.h>
 #include <linux/slab.h>
+#include <linux/workqueue.h>
 
 /* USB HID defines */
 #define USB_REQ_GET_REPORT		0x01