drivers/gpio/it8761e_gpio: check return value of gpiochip_remove()

This eliminates the following build warning:

drivers/gpio/it8761e_gpio.c: In function `it8761e_gpio_exit':
drivers/gpio/it8761e_gpio.c:220: warning: ignoring return value of `gpiochip_remove', declared with attribute warn_unused_result

Signed-off-by: Daniel Mack <daniel@caiaq.de>
Cc: Denis Turischev <denis@compulab.co.il>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>