gpio: EN7523: fix kernel-doc warnings

Add "struct" keyword and explain the @dir array differently to
prevent kernel-doc warnings:

gpio-en7523.c:22: warning: cannot understand function prototype: 'struct airoha_gpio_ctrl '
gpio-en7523.c:27: warning: Function parameter or struct member 'dir' not described in 'airoha_gpio_ctrl'
gpio-en7523.c:27: warning: Excess struct member 'dir0' description in 'airoha_gpio_ctrl'
gpio-en7523.c:27: warning: Excess struct member 'dir1' description in 'airoha_gpio_ctrl'

Fixes: 0868ad38 ("gpio: Add support for Airoha EN7523 GPIO controller")
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>

drivers/gpio/gpio-en7523.c

@@ -12,11 +12,11 @@
 #define AIROHA_GPIO_MAX		32
 
 /**
- * airoha_gpio_ctrl - Airoha GPIO driver data
+ * struct airoha_gpio_ctrl - Airoha GPIO driver data
  * @gc: Associated gpio_chip instance.
  * @data: The data register.
- * @dir0: The direction register for the lower 16 pins.
- * @dir1: The direction register for the higher 16 pins.
+ * @dir: [0] The direction register for the lower 16 pins.
+ * [1]: The direction register for the higher 16 pins.
  * @output: The output enable register.
  */
 struct airoha_gpio_ctrl {