[media] cx231xx: get rid of warning: no previous prototype

drivers/media/usb/cx231xx/cx231xx-avcore.c:1071:5: warning: no previous prototype for 'stopAudioFirmware' [-Wmissing-prototypes]
drivers/media/usb/cx231xx/cx231xx-avcore.c:1076:5: warning: no previous prototype for 'restartAudioFirmware' [-Wmissing-prototypes]
drivers/media/usb/cx231xx/cx231xx-cards.c:689:6: warning: no previous prototype for 'cx231xx_reset_out' [-Wmissing-prototypes]
drivers/media/usb/cx231xx/cx231xx-cards.c:697:6: warning: no previous prototype for 'cx231xx_enable_OSC' [-Wmissing-prototypes]
drivers/media/usb/cx231xx/cx231xx-cards.c:701:6: warning: no previous prototype for 'cx231xx_sleep_s5h1432' [-Wmissing-prototypes]
drivers/media/usb/cx231xx/cx231xx-i2c.c:75:5: warning: no previous prototype for 'cx231xx_i2c_send_bytes' [-Wmissing-prototypes]

Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
diff --git a/drivers/media/usb/cx231xx/cx231xx-cards.c b/drivers/media/usb/cx231xx/cx231xx-cards.c
index b84ebc5..bbed1e4 100644
--- a/drivers/media/usb/cx231xx/cx231xx-cards.c
+++ b/drivers/media/usb/cx231xx/cx231xx-cards.c
@@ -686,7 +686,7 @@
 }
 EXPORT_SYMBOL_GPL(cx231xx_tuner_callback);
 
-void cx231xx_reset_out(struct cx231xx *dev)
+static void cx231xx_reset_out(struct cx231xx *dev)
 {
 	cx231xx_set_gpio_value(dev, CX23417_RESET, 1);
 	msleep(200);
@@ -694,11 +694,13 @@
 	msleep(200);
 	cx231xx_set_gpio_value(dev, CX23417_RESET, 1);
 }
-void cx231xx_enable_OSC(struct cx231xx *dev)
+
+static void cx231xx_enable_OSC(struct cx231xx *dev)
 {
 	cx231xx_set_gpio_value(dev, CX23417_OSC_EN, 1);
 }
-void cx231xx_sleep_s5h1432(struct cx231xx *dev)
+
+static void cx231xx_sleep_s5h1432(struct cx231xx *dev)
 {
 	cx231xx_set_gpio_value(dev, SLEEP_S5H1432, 0);
 }