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/renesas/sh7757lcr/sh7757lcr.c b/board/renesas/sh7757lcr/sh7757lcr.c
index 0a04a9d..3f970fc 100644
--- a/board/renesas/sh7757lcr/sh7757lcr.c
+++ b/board/renesas/sh7757lcr/sh7757lcr.c
@@ -278,10 +278,10 @@
 	for (i = 0; i < SH7757LCR_ETHERNET_NUM_CH; i++) {
 		get_sh_eth_mac(i, mac_string, buf);
 		if (i == 0)
-			setenv("ethaddr", mac_string);
+			env_set("ethaddr", mac_string);
 		else {
 			sprintf(env_string, "eth%daddr", i);
-			setenv(env_string, mac_string);
+			env_set(env_string, mac_string);
 		}
 
 		set_mac_to_sh_eth_register(i, mac_string);
@@ -291,7 +291,7 @@
 	for (i = 0; i < SH7757LCR_GIGA_ETHERNET_NUM_CH; i++) {
 		get_sh_eth_mac(i + SH7757LCR_ETHERNET_NUM_CH, mac_string, buf);
 		sprintf(env_string, "eth%daddr", i + SH7757LCR_ETHERNET_NUM_CH);
-		setenv(env_string, mac_string);
+		env_set(env_string, mac_string);
 
 		set_mac_to_sh_giga_eth_register(i, mac_string);
 	}