common: Move command functions out of common.h

Move these functions into the command.h header file which is a better fit.

Signed-off-by: Simon Glass <sjg@chromium.org>
Reviewed-by: Tom Rini <trini@konsulko.com>
diff --git a/test/dm/sf.c b/test/dm/sf.c
index 65aab4f..7805af7 100644
--- a/test/dm/sf.c
+++ b/test/dm/sf.c
@@ -4,6 +4,7 @@
  */
 
 #include <common.h>
+#include <command.h>
 #include <dm.h>
 #include <fdtdec.h>
 #include <mapmem.h>