fix compile warning for env tools

Patch fixes this issue:

fw_env.c: In function ‘fw_setenv’:
fw_env.c:492:5: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 3 has type ‘size_t’ [-Wformat]
fw_env.c: In function ‘flash_write_buf’:
fw_env.c:806:6: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 3 has type ‘size_t’ [-Wformat]

Signed-off-by: Luka Perkov <lists@lukaperkov.net>
Acked-by: Mike Frysinger <vapier@gentoo.org>

tools/env/fw_env.c

@@ -488,7 +488,7 @@ int fw_setenv(int argc, char *argv[])
 			value = (char *)malloc(len - strlen(name));
 			if (!value) {
 				fprintf(stderr,
-				"Cannot malloc %u bytes: %s\n",
+				"Cannot malloc %zu bytes: %s\n",
 				len - strlen(name), strerror(errno));
 				return -1;
 			}
@@ -802,7 +802,7 @@ static int flash_write_buf (int dev, int fd, void *buf, size_t count,
 		data = malloc (erase_len);
 		if (!data) {
 			fprintf (stderr,
-				 "Cannot malloc %u bytes: %s\n",
+				 "Cannot malloc %zu bytes: %s\n",
 				 erase_len, strerror (errno));
 			return -1;
 		}