gpio: Correct kernel-doc inconsistency

Fix kernel-doc comment to match parameter name change "chip" to "gc"
in gpiochip_add_data function.

Signed-off-by: Colton Lewis <colton.w.lewis@protonmail.com>
Link: https://lore.kernel.org/r/20200723095658.234668-1-colton.w.lewis@protonmail.com


Signed-off-by: Linus Walleij <linus.walleij@linaro.org>