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/drivers/serial/Kconfig b/drivers/serial/Kconfig
index af01e50..286c998 100644
--- a/drivers/serial/Kconfig
+++ b/drivers/serial/Kconfig
@@ -825,6 +825,11 @@
 
 endchoice
 
+config SH_SCIF_CLK_FREQ
+	int "SCIF console clock frequency"
+	depends on SCIF_CONSOLE && (!DM_SERIAL || (SPL && !SPL_DM_SERIAL))
+	default 65000000
+
 config SEMIHOSTING_SERIAL
 	bool "Semihosting UART support"
 	depends on SEMIHOSTING && !SERIAL_RX_BUFFER