gpio: syscon: fix excess struct member build warning

Fix the build warning with W=1 flag,
"Excess struct member 'compatible' description in 'syscon_gpio_data' "
by removing the documentation for the non existent member.

Signed-off-by: Dhruva Gole <d-gole@ti.com>
Link: https://lore.kernel.org/r/20240902-b4-gpio-fix-v1-1-49a997994fa5@ti.com


Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>