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/arch/arm/mach-imx/mx6/opos6ul.c b/arch/arm/mach-imx/mx6/opos6ul.c
index 22b2440..f8d7e8e 100644
--- a/arch/arm/mach-imx/mx6/opos6ul.c
+++ b/arch/arm/mach-imx/mx6/opos6ul.c
@@ -132,7 +132,7 @@
 	/* In bootstrap don't use the env vars */
 	if (((reg & 0x3000000) >> 24) == 0x1) {
 		set_default_env(NULL);
-		setenv("preboot", "");
+		env_set("preboot", "");
 	}
 
 	return opos6ul_board_late_init();
diff --git a/arch/arm/mach-imx/mx7/soc.c b/arch/arm/mach-imx/mx7/soc.c
index 4cf977e..7152c84 100644
--- a/arch/arm/mach-imx/mx7/soc.c
+++ b/arch/arm/mach-imx/mx7/soc.c
@@ -256,9 +256,9 @@
 {
 #ifdef CONFIG_ENV_VARS_UBOOT_RUNTIME_CONFIG
 	if (is_mx7d())
-		setenv("soc", "imx7d");
+		env_set("soc", "imx7d");
 	else
-		setenv("soc", "imx7s");
+		env_set("soc", "imx7s");
 #endif
 
 	return 0;