Mark functions as static. From @howard0su (part of PR #571)

Author: PhracturedBlue

src/pages/128x64x1/scanner_page.c

@@ -43,7 +43,7 @@ static const char *attstr_cb(guiObject_t *obj, const void *data)
     return sp->attenuator ? _tr("-20dB") : _tr("0dB");
 }
 
-void _draw_page(u8 enable)
+static void _draw_page(u8 enable)
 {
     (void)enable;
     PAGE_ShowHeader(PAGE_GetName(PAGEID_SCANNER));

src/pages/320x240x16/scanner_page.c

@@ -49,7 +49,7 @@ static const char *attstr_cb(guiObject_t *obj, const void *data)
     return sp->attenuator ? _tr("Att.: -20dB") : _tr("Att.: 0dB");
 }
 
-void _draw_page(u8 enable)
+static void _draw_page(u8 enable)
 {
     enum {
         SCANBARWIDTH   = (LCD_WIDTH / (MAX_RADIOCHANNEL - MIN_RADIOCHANNEL + 1)),

src/pages/common/advanced/_mixer_page.c

@@ -143,7 +143,7 @@ static void reorder_return_cb(u8 *list)
     }
 }
 
-void reorder_cb(guiObject_t *obj, const void *data)
+static void reorder_cb(guiObject_t *obj, const void *data)
 {
     (void)data;
     (void)obj;

src/pages/common/advanced/_mixer_setup.c

@@ -560,7 +560,7 @@ static void reorder_return_cb(u8 *list)
     }
 }
 
-void reorder_cb(guiObject_t *obj, void *data)
+static void reorder_cb(guiObject_t *obj, void *data)
 {
     (void)data;
     (void)obj;