env: Rename setenv() to env_set()

We are now using an env_ prefix for environment functions. Rename setenv()
for consistency. Also add function comments in common.h.

Suggested-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/freescale/mx6sabreauto/mx6sabreauto.c b/board/freescale/mx6sabreauto/mx6sabreauto.c
index a5703a3..ea78091 100644
--- a/board/freescale/mx6sabreauto/mx6sabreauto.c
+++ b/board/freescale/mx6sabreauto/mx6sabreauto.c
@@ -687,14 +687,14 @@
 #endif
 
 #ifdef CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
-	setenv("board_name", "SABREAUTO");
+	env_set("board_name", "SABREAUTO");
 
 	if (is_mx6dqp())
-		setenv("board_rev", "MX6QP");
+		env_set("board_rev", "MX6QP");
 	else if (is_mx6dq())
-		setenv("board_rev", "MX6Q");
+		env_set("board_rev", "MX6Q");
 	else if (is_mx6sdl())
-		setenv("board_rev", "MX6DL");
+		env_set("board_rev", "MX6DL");
 #endif
 
 	return 0;