cyclic: Add a symbol for SPL

The cyclic subsystem is currently enabled either in all build phases
or none. For tools this should not be enabled, but since lib/shc256.c
and other files include watchdog.h in the host build, we must make
sure that it is not enabled there.

Add an SPL symbol so that there is more control of this.

Add an include into cyclic.h so that tools can include this file.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Devarsh Thakkar <devarsht@ti.com>
Reviewed-by: Stefan Roese <sr@denx.de>
diff --git a/include/asm-generic/global_data.h b/include/asm-generic/global_data.h
index aa336d6..27aa75e 100644
--- a/include/asm-generic/global_data.h
+++ b/include/asm-generic/global_data.h
@@ -481,7 +481,7 @@
 	 */
 	struct event_state event_state;
 #endif
-#ifdef CONFIG_CYCLIC
+#if CONFIG_IS_ENABLED(CYCLIC)
 	/**
 	 * @cyclic_list: list of registered cyclic functions
 	 */