env: Rename the redundancy flags

Add an ENV prefix to these two flags so that it is clear what they relate
to. Also move them to env.h since they are part of the public API. Use an
enum rather than a #define to tie them together.

Signed-off-by: Simon Glass <sjg@chromium.org>

cmd/nvedit.c

@@ -1002,7 +1002,7 @@ NXTARG:		;
 		envp->crc = crc32(0, envp->data,
 				size ? size - offsetof(env_t, data) : ENV_SIZE);
 #ifdef CONFIG_ENV_ADDR_REDUND
-		envp->flags = ACTIVE_FLAG;
+		envp->flags = ENV_REDUND_ACTIVE;
 #endif
 	}
 	env_set_hex("filesize", len + offsetof(env_t, data));