staging: nvec: Include missing headers

Those headers were apparently included by other headers
previously, but are not anymore.
Signed-off-by: Julian Andres Klode <jak@jak-linux.org>
Acked-by: Marc Dietrich <marvin24@gmx.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

drivers/staging/nvec/nvec.h

 #ifndef __LINUX_MFD_NVEC
 #define __LINUX_MFD_NVEC
 
+#include <linux/notifier.h>
 #include <linux/semaphore.h>
 
 typedef enum {

drivers/staging/nvec/nvec_kbd.c

+#include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/input.h>
 #include <linux/delay.h>

drivers/staging/nvec/nvec_ps2.c

+#include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/serio.h>
 #include <linux/delay.h>