[MTD] [NAND] Fix missing kernel-doc

[Reported by Randy Dunlap]

Signed-off-by: Alexey Korolev <akorolev@infradead.org>
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
diff --git a/include/linux/mtd/nand.h b/include/linux/mtd/nand.h
index 81774e5..733d3f3 100644
--- a/include/linux/mtd/nand.h
+++ b/include/linux/mtd/nand.h
@@ -248,6 +248,7 @@
  * @read_page_raw:	function to read a raw page without ECC
  * @write_page_raw:	function to write a raw page without ECC
  * @read_page:	function to read a page according to the ecc generator requirements
+ * @read_subpage:	function to read parts of the page covered by ECC.
  * @write_page:	function to write a page according to the ecc generator requirements
  * @read_oob:	function to read chip OOB data
  * @write_oob:	function to write chip OOB data