MAINTAINERS: Add Segey Semin to maintainers of DW APB GPIO driver

Add myself as a co-maintainer of the Synopsis DesignWare APB GPIO driver.

Suggested-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Cc: Hoan Tran <hoan@os.amperecomputing.com>
Cc: Alexey Malahov <Alexey.Malahov@baikalelectronics.ru>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Paul Burton <paulburton@kernel.org>
Cc: Ralf Baechle <ralf@linux-mips.org>
Cc: linux-gpio@vger.kernel.org
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Link: https://lore.kernel.org/r/20200323195401.30338-7-Sergey.Semin@baikalelectronics.ru


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>