MAINTAINERS: add entry for Denali NAND controller driver

The Denali NAND controller driver (drivers/mtd/nand/denali*) has been
largely reworked by me.  Add myself as its maintainer now.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Boris Brezillon <boris.brezillon@free-electrons.com>

MAINTAINERS

@@ -3888,6 +3888,12 @@ M:	Pali Rohár <pali.rohar@gmail.com>
 S:	Maintained
 F:	drivers/platform/x86/dell-wmi.c
 
+DENALI NAND DRIVER
+M:	Masahiro Yamada <yamada.masahiro@socionext.com>
+L:	linux-mtd@lists.infradead.org
+S:	Supported
+F:	drivers/mtd/nand/denali*
+
 DESIGNWARE USB2 DRD IP DRIVER
 M:	John Youn <johnyoun@synopsys.com>
 L:	linux-usb@vger.kernel.org