Kconfig: move CONFIG_SYS_CLK_FREQ to Kconfig

It makes sense to specify CONFIG_SYS_CLK_FREQ in "configs/xx_defconfig"
instead of "include/configs/xxx.h" because then header will be reusable
across boards with different CPU clocks.

Also this nice to have an ability for end user to tune this value
himself via "menuconfig".

For now I'm only applying this change to all ARC configs because
otherwise scope of change will be huge.

Signed-off-by: Alexey Brodkin <abrodkin@synopsys.com>
Cc: Tom Rini <trini@ti.com>
Cc: Masahiro Yamada <yamada.m@jp.panasonic.com>
Cc: Hans de Goede <hdegoede@redhat.com>
cc: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@ti.com>
diff --git a/Kconfig b/Kconfig
index 60cf1dd..4157da3 100644
--- a/Kconfig
+++ b/Kconfig
@@ -143,6 +143,12 @@
 	help
 	  TODO: Move CONFIG_SYS_TEXT_BASE for all the architecture
 
+config SYS_CLK_FREQ
+	depends on ARC
+	int "CPU clock frequency"
+	help
+	  TODO: Move CONFIG_SYS_CLK_FREQ for all the architecture
+
 endmenu		# Boot images
 
 source "arch/Kconfig"