gpio: imx-scu: Use ARRAY_SIZE for array length

Use of macro ARRAY_SIZE to calculate array size minimizes
the redundant code and improves code reusability.
This fixes warnings reported by Coccinelle:
drivers/gpio/gpio-imx-scu.c:106:32-33: WARNING: Use ARRAY_SIZE

Signed-off-by: Rajeshwar R Shinde <coolrrsh@gmail.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>