libfs: use generic_file_llseek for simple_attr

Simple attribute files need to be seekable to
allow resetting the file for another read.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 76041b6..c8effc8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2450,6 +2450,7 @@
 	.release = simple_attr_release,					\
 	.read	 = simple_attr_read,					\
 	.write	 = simple_attr_write,					\
+	.llseek	 = generic_file_llseek,					\
 };
 
 static inline void __attribute__((format(printf, 1, 2)))