gpio: aspeed-sgpio: fixed typos

This fixes some various typos.

Signed-off-by: Sachin Agarwal <asachin591@gmail.com>
Link: https://lore.kernel.org/r/20200118105319.68637-1-sachinagarwal@sachins-MacBook-2.local


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