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/net/arp.c b/net/arp.c
index f3ceff9..4c79e09 100644
--- a/net/arp.c
+++ b/net/arp.c
@@ -194,7 +194,7 @@
 		if (net_server_ip.s_addr == net_arp_wait_packet_ip.s_addr) {
 			char buf[20];
 			sprintf(buf, "%pM", &arp->ar_sha);
-			setenv("serveraddr", buf);
+			env_set("serveraddr", buf);
 		}
 #endif
 
diff --git a/net/bootp.c b/net/bootp.c
index be8f710..5795156 100644
--- a/net/bootp.c
+++ b/net/bootp.c
@@ -170,7 +170,7 @@
 	 * not contain a new value
 	 */
 	if (*net_boot_file_name)
-		setenv("bootfile", net_boot_file_name);
+		env_set("bootfile", net_boot_file_name);
 #endif
 	net_copy_ip(&net_ip, &bp->bp_yiaddr);
 }
diff --git a/net/dns.c b/net/dns.c
index 7017bac..eee8a02 100644
--- a/net/dns.c
+++ b/net/dns.c
@@ -184,7 +184,7 @@
 			ip_to_string(ip_addr, ip_str);
 			printf("%s\n", ip_str);
 			if (net_dns_env_var)
-				setenv(net_dns_env_var, ip_str);
+				env_set(net_dns_env_var, ip_str);
 		} else {
 			puts("server responded with invalid IP number\n");
 		}
diff --git a/net/eth_common.c b/net/eth_common.c
index 58fa295..ef97da7 100644
--- a/net/eth_common.c
+++ b/net/eth_common.c
@@ -39,7 +39,7 @@
 
 	sprintf(buf, "%pM", enetaddr);
 
-	return setenv(name, buf);
+	return env_set(name, buf);
 }
 
 int eth_getenv_enetaddr_by_index(const char *base_name, int index,
@@ -97,14 +97,14 @@
 	/* update current ethernet name */
 	if (eth_get_dev()) {
 		if (act == NULL || strcmp(act, eth_get_name()) != 0)
-			setenv("ethact", eth_get_name());
+			env_set("ethact", eth_get_name());
 	}
 	/*
 	 * remove the variable completely if there is no active
 	 * interface
 	 */
 	else if (act != NULL)
-		setenv("ethact", NULL);
+		env_set("ethact", NULL);
 }
 
 void eth_try_another(int first_restart)