MAINTAINERS: Add maintainers for DWC AHCI SATA driver

Add myself as a maintainer of the new DWC AHCI SATA driver and
its DT-bindings schema.

Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Signed-off-by: Damien Le Moal <damien.lemoal@opensource.wdc.com>