env: Rename common functions related to setenv()

We are now using an env_ prefix for environment functions. Rename these
commonly used functions, 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/cmd/load.c b/cmd/load.c
index 4597ec5..ec3730e 100644
--- a/cmd/load.c
+++ b/cmd/load.c
@@ -182,7 +182,7 @@
 			    start_addr, end_addr, size, size
 		    );
 		    flush_cache(start_addr, size);
-		    setenv_hex("filesize", size);
+		    env_set_hex("filesize", size);
 		    return (addr);
 		case SREC_START:
 		    break;
@@ -529,7 +529,7 @@
 	flush_cache(offset, size);
 
 	printf("## Total Size      = 0x%08x = %d Bytes\n", size, size);
-	setenv_hex("filesize", size);
+	env_set_hex("filesize", size);
 
 	return offset;
 }
@@ -1000,7 +1000,7 @@
 	flush_cache(offset, ALIGN(size, ARCH_DMA_MINALIGN));
 
 	printf("## Total Size      = 0x%08x = %d Bytes\n", size, size);
-	setenv_hex("filesize", size);
+	env_set_hex("filesize", size);
 
 	return offset;
 }