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>