MAINTAINERS: add me as a maintainer of UBI

Add me for UBI custodian.

Signed-off-by: Heiko Schocher <hs@denx.de>
Acked-by: Stefan Roese <sr@denx.de>
Acked-by: Kyungmin Park <kyungmin.park@samsung.com>
diff --git a/doc/git-mailrc b/doc/git-mailrc
index ad22763..69fe443 100644
--- a/doc/git-mailrc
+++ b/doc/git-mailrc
@@ -119,6 +119,7 @@
 alias nand           uboot, scottwood
 alias net            uboot, jhersh
 alias spi	     uboot, jagan
+alias ubi            uboot, hs
 alias usb            uboot, marex
 alias video          uboot, ag
 alias patman         uboot, sjg