serial: sc16is7xx: fix implicit decl of func copy_{to,from}_user

Fix by including linux/uaccess.h:

   drivers/tty/serial/sc16is7xx.c: In function 'sc16is7xx_ioctl':
>> drivers/tty/serial/sc16is7xx.c:861:3: error: implicit declaration of function 'copy_from_user' [-Werror=implicit-function-declaration]
>> drivers/tty/serial/sc16is7xx.c:867:3: error: implicit declaration of function 'copy_to_user' [-Werror=implicit-function-declaration]

Signed-off-by: Jon Ringle <jringle@gridpoint.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/tty/serial/sc16is7xx.c

@@ -25,6 +25,7 @@
 #include <linux/serial.h>
 #include <linux/tty.h>
 #include <linux/tty_flip.h>
+#include <linux/uaccess.h>
 
 #define SC16IS7XX_NAME			"sc16is7xx"