common: commands: make commands static

Since most commands are not public, make them static. This
prevents warnings that no common prototype is available.

Signed-off-by: Jeroen Hofstee <jeroen@myspectrum.nl>
diff --git a/common/cmd_source.c b/common/cmd_source.c
index f3e9e60..6881bc9 100644
--- a/common/cmd_source.c
+++ b/common/cmd_source.c
@@ -142,8 +142,7 @@
 
 /**************************************************/
 #if defined(CONFIG_CMD_SOURCE)
-int
-do_source (cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+static int do_source(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
 {
 	ulong addr;
 	int rcode;