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_i2c.c b/common/cmd_i2c.c
index d714658..3a75f94 100644
--- a/common/cmd_i2c.c
+++ b/common/cmd_i2c.c
@@ -1366,7 +1366,8 @@
  * Returns zero always.
  */
 #if defined(CONFIG_SYS_I2C)
-int do_i2c_show_bus(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+static int do_i2c_show_bus(cmd_tbl_t *cmdtp, int flag, int argc,
+				char * const argv[])
 {
 	int	i;
 #ifndef CONFIG_SYS_I2C_DIRECT_BUS
@@ -1425,7 +1426,8 @@
  * on error.
  */
 #if defined(CONFIG_SYS_I2C) || defined(CONFIG_I2C_MULTI_BUS)
-int do_i2c_bus_num(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
+static int do_i2c_bus_num(cmd_tbl_t *cmdtp, int flag, int argc,
+				char * const argv[])
 {
 	int		ret = 0;
 	unsigned int	bus_no;