MAINTAINERS: Fix file name for DesignWare GPIO DT schema

MAINTAINERS: Fix file name for DesignWare GPIO DT schema

The commit 4ac0edc593d2
  ("dt-bindings: gpio: Convert snps,dw-apb-gpio to DT schema")
missed MAINTAINERS update.

Fixes: 4ac0edc593d2 ("dt-bindings: gpio: Convert snps,dw-apb-gpio to DT schema")
Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Reviewed-by: Serge Semin <fancer.lancer@gmail.com>
Cc: Serge Semin <Sergey.Semin@baikalelectronics.ru>
Link: https://lore.kernel.org/r/20200520120955.68427-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>