MAINTAINERS: add zx2967 reset controller driver to ARM ZTE architecture

Add the zx2967 reset controller driver as maintained by ARM ZTE
architecture maintainers, as they're parts of the core IP.

Signed-off-by: Baoyou Xie <baoyou.xie@linaro.org>
Signed-off-by: Philipp Zabel <p.zabel@pengutronix.de>