[ARM] Fix nwbutton sparse warnings

drivers/char/nwbutton.c:177:24: warning: incorrect type in argument 1 (different address spaces)/home/rmk/bk/linux-2.6-rmk/drivers/char/nwbutton.c:177:24:    expected void [noderef] *to<asn:1>
drivers/char/nwbutton.c:177:24:    got char *buffer
drivers/char/nwbutton.c:177:24: warning: incorrect type in initializer (different address spaces)
drivers/char/nwbutton.c:177:24:    expected void [noderef] *to<asn:1>
drivers/char/nwbutton.c:177:24:    got char *buffer
drivers/char/nwbutton.c:189:11: warning: incorrect type in initializer (incompatible argument 2 (different address spaces))
drivers/char/nwbutton.c:189:11:    expected int [usertype] ( *read )( ... )
drivers/char/nwbutton.c:189:11:    got int ( static [addressable] [toplevel] *<noident> )( ... )

drivers/char/nwbutton.c

@@ -170,7 +170,7 @@ static irqreturn_t button_handler (int irq, void *dev_id, struct pt_regs *regs)
  * device at any one time.
  */
 
-static int button_read (struct file *filp, char *buffer,
+static int button_read (struct file *filp, char __user *buffer,
 			size_t count, loff_t *ppos)
 {
 	interruptible_sleep_on (&button_wait_queue);

drivers/char/nwbutton.h

@@ -26,8 +26,6 @@ struct button_callback {
 
 static void button_sequence_finished (unsigned long parameters);
 static irqreturn_t button_handler (int irq, void *dev_id, struct pt_regs *regs);
-static int button_read (struct file *filp, char *buffer,
-			size_t count, loff_t *ppos);
 int button_init (void);
 int button_add_callback (void (*callback) (void), int count);
 int button_del_callback (void (*callback) (void));