env: Rename getenv/_f() to env_get()

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

Quite a few places use getenv() in a condition context, provoking a
warning from checkpatch. These are fixed up in this patch also.

Suggested-by: Wolfgang Denk <wd@denx.de>
Signed-off-by: Simon Glass <sjg@chromium.org>
diff --git a/board/BuR/common/common.c b/board/BuR/common/common.c
index eb34de9..39a600b 100644
--- a/board/BuR/common/common.c
+++ b/board/BuR/common/common.c
@@ -263,9 +263,9 @@
 				(size_t *)&dtbsize,
 				NULL, 0x20000, (u_char *)dtbaddr);
 #else
-	char *dtbname = getenv("dtb");
-	char *dtbdev = getenv("dtbdev");
-	char *dtbpart = getenv("dtbpart");
+	char *dtbname = env_get("dtb");
+	char *dtbdev = env_get("dtbdev");
+	char *dtbpart = env_get("dtbpart");
 	if (!dtbdev || !dtbpart || !dtbname) {
 		printf("%s: <dtbdev>/<dtbpart>/<dtb> missing.\n", __func__);
 		return -1;
@@ -405,11 +405,11 @@
 				       char *name, char *altname,
 				       char *suffix)
 {
-	char *envval = getenv(name);
+	char *envval = env_get(name);
 	if (0 != envval) {
 		lcd_printf("%s %s %s", prefix, envval, suffix);
 	} else if (0 != altname) {
-		envval = getenv(altname);
+		envval = env_get(altname);
 		if (0 != envval)
 			lcd_printf("%s %s %s", prefix, envval, suffix);
 	} else {
@@ -657,7 +657,7 @@
 	mac_addr[4] = mac_lo & 0xFF;
 	mac_addr[5] = (mac_lo & 0xFF00) >> 8;
 
-	if (!getenv("ethaddr")) {
+	if (!env_get("ethaddr")) {
 		#if !defined(CONFIG_SPL_BUILD) && defined(CONFIG_USE_FDT)
 		printf("<ethaddr> not set. trying DTB ... ");
 		mac = dtbmacaddr(0);