cleanup: Use static functions for non-declared methods

libfprint/drivers/aes2501.c

@@ -686,7 +686,7 @@ enum activate_states {
   ACTIVATE_NUM_STATES,
 };
 
-void
+static void
 activate_read_regs_cb (FpImageDevice *dev, GError *error,
                        unsigned char *regs, void *user_data)
 {

libfprint/drivers/elan.c

@@ -41,7 +41,7 @@
 #include "drivers_api.h"
 #include "elan.h"
 
-unsigned char
+static unsigned char
 elan_get_pixel (struct fpi_frame_asmbl_ctx *ctx,
                 struct fpi_frame *frame, unsigned int x,
                 unsigned int y)
@@ -91,7 +91,7 @@ G_DECLARE_FINAL_TYPE (FpiDeviceElan, fpi_device_elan, FPI, DEVICE_ELAN,
                       FpImageDevice);
 G_DEFINE_TYPE (FpiDeviceElan, fpi_device_elan, FP_TYPE_IMAGE_DEVICE);
 
-int
+static int
 cmp_short (const void *a, const void *b)
 {
   return (int) (*(short *) a - *(short *) b);

libfprint/fp-device.c

@@ -1386,7 +1386,7 @@ typedef struct
   FpDevice *device;
 } FpDeviceTimeoutSource;
 
-void
+static void
 timeout_finalize (GSource *source)
 {
   FpDeviceTimeoutSource *timeout_source = (FpDeviceTimeoutSource *) source;

libfprint/fpi-usb-transfer.c

@@ -298,7 +298,7 @@ fpi_usb_transfer_fill_interrupt_full (FpiUsbTransfer *transfer,
   transfer->free_buffer = free_func;
 }
 
-void
+static void
 transfer_finish_cb (GObject *source_object, GAsyncResult *res, gpointer user_data)
 {
   GError *error = NULL;