MAINTAINERS: Update i.MX 8QXP ADC info

Update my email address to use developer mail address,
because the old address will be dropped soon.

And change the status from 'Supported' to 'Maintained' for me
to look after this code without any payment now.

Signed-off-by: Cai Huoqing <caihuoqing@baidu.com>
Link: https://lore.kernel.org/r/20211201083100.1587-1-caihuoqing@baidu.com


Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>