spi: meson: meson_spifc_setup_speed() can be static

drivers/spi/spi-meson-spifc.c:171:6: sparse: symbol 'meson_spifc_setup_speed' was not declared. Should it be static?
Signed-off-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Mark Brown <broonie@kernel.org>

drivers/spi/spi-meson-spifc.c

@@ -168,7 +168,7 @@ static void meson_spifc_fill_buffer(struct meson_spifc *spifc, const u8 *buf,
  * @spifc:	the Meson SPI device
  * @speed:	desired speed in Hz
  */
-void meson_spifc_setup_speed(struct meson_spifc *spifc, u32 speed)
+static void meson_spifc_setup_speed(struct meson_spifc *spifc, u32 speed)
 {
 	unsigned long parent, value;
 	int n;