gpio: sysfs: drop tabs from local variable declarations

Older code has an annoying habit of putting tabs between the type and the
name of the variable. This doesn't really add to readability and newer
code doesn't do it so make the entire file consistent.

Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>
Reviewed-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>