Convert CONFIG_SH_SCIF_CLK_FREQ to Kconfig

This converts the following to Kconfig:
   CONFIG_SH_SCIF_CLK_FREQ

Signed-off-by: Tom Rini <trini@konsulko.com>
diff --git a/configs/stout_defconfig b/configs/stout_defconfig
index 0502ae5..ea07ceb 100644
--- a/configs/stout_defconfig
+++ b/configs/stout_defconfig
@@ -88,6 +88,7 @@
 CONFIG_DM_REGULATOR_FIXED=y
 CONFIG_DM_REGULATOR_GPIO=y
 CONFIG_SCIF_CONSOLE=y
+CONFIG_SH_SCIF_CLK_FREQ=52000000
 CONFIG_SPI=y
 CONFIG_DM_SPI=y
 CONFIG_SH_QSPI=y