shell: fix mufs cat to write contents to the appropriate serial interface

source/shell/mufs.c

@@ -161,7 +161,7 @@ static void do_mufs_cat(FILE *out, const char **argv, size_t argc)
 	}
 
 	while (mufs_read(file, data, sizeof data) != 0) {
-		fwrite(data, sizeof *data, sizeof data, stdout);
+		fwrite(data, sizeof *data, sizeof data, out);
 	}
 
 	mufs_close(file);