gpio: timberdale: repair kernel-doc comments

gpio: timberdale: repair kernel-doc comments

Use a ':' after struct member names to avoid kernel-doc warnings:

Warning: include/linux/timb_gpio.h:22 struct member 'gpio_base' not
 described in 'timbgpio_platform_data'
Warning: include/linux/timb_gpio.h:22 struct member 'nr_pins' not
 described in 'timbgpio_platform_data'
Warning: include/linux/timb_gpio.h:22 struct member 'irq_base' not
 described in 'timbgpio_platform_data'

Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Link: https://patch.msgid.link/20260301014822.3133268-1-rdunlap@infradead.org
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@oss.qualcomm.com>