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/board/samsung/common/misc.c b/board/samsung/common/misc.c
index 3ef1e79..9117669 100644
--- a/board/samsung/common/misc.c
+++ b/board/samsung/common/misc.c
@@ -5,6 +5,7 @@
  */
 
 #include <common.h>
+#include <command.h>
 #include <env.h>
 #include <lcd.h>
 #include <libtizen.h>