Change bcmring Maintainer list.

I am Jiandong Zheng working on BCMRING in Broadcom Canada Ltd. I am
replacing Leo Chen (leochen@broadcom.com) as "ARM/BCMRING ARM
ARCHITECTURE" and "ARM/BCMRING MTD NAND DRIVER" maintainer from
Broadcom as he is no longer the maintainer of these components.

Signed-off-by: Jiandong Zheng <jdzheng@broadcom.com>
Acked-by: Scott Branden <sbranden@broadcom.com>
Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>