gpiolib: acpi: Correct kernel doc of struct acpi_gpio_event

The checker complains during build

gpiolib-acpi.c:45: warning: Function parameter or member 'irq_requested' not described in 'acpi_gpio_event'

because the typo in the field description.

Fix the name to have documentation up-to-date.

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Acked-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>