Input: focaltech - mark focaltech_set_resolution() static

We get 1 warning when building kernel with W=1:
drivers/input/mouse/focaltech.c:393:6: warning: no previous prototype for 'focaltech_set_resolution' [-Wmissing-prototypes]

In fact, this function is only used in the file in which it is
declared and don't need a declaration, but can be made static.
So this patch marks it 'static'.
Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
Acked-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>

drivers/input/mouse/focaltech.c

@@ -390,7 +390,8 @@ static int focaltech_read_size(struct psmouse *psmouse)
 	return 0;
 }
 
-void focaltech_set_resolution(struct psmouse *psmouse, unsigned int resolution)
+static void focaltech_set_resolution(struct psmouse *psmouse,
+				     unsigned int resolution)
 {
 	/* not supported yet */
 }