MAINTAINERS: add maintainer for ADA4250 driver

Add myself as maintainer for the ADA4250 driver.

Signed-off-by: Antoniu Miclaus <antoniu.miclaus@analog.com>
Link: https://lore.kernel.org/r/20220223120112.8067-3-antoniu.miclaus@analog.com


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