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: 0868ad385aff ("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>

gpio: Add support for Airoha EN7523 GPIO controller

Airoha's GPIO controller on their ARM EN7523 SoCs consists of two banks of 32
GPIOs. Each instance in DT is for a single bank.

Acked-by: Bartosz Golaszewski <brgl@bgdev.pl>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
Signed-off-by: John Crispin <john@phrozen.org>
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Signed-off-by: Bartosz Golaszewski <brgl@bgdev.pl>