MAINTAINERS: Update Intel 8255 GPIO driver file list

The drivers/gpio/gpio-i8255.h header file is also maintained.

Signed-off-by: William Breathitt Gray <william.gray@linaro.org>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>

Author: William Breathitt Gray

MAINTAINERS

@@ -9907,6 +9907,7 @@ M:	William Breathitt Gray <william.gray@linaro.org>
 L:	linux-gpio@vger.kernel.org
 S:	Maintained
 F:	drivers/gpio/gpio-i8255.c
+F:	drivers/gpio/gpio-i8255.h
 
 INTEL ASoC DRIVERS
 M:	Cezary Rojewski <cezary.rojewski@intel.com>