gpio: removing kfree remove functionality

commit 3de07e5aaf290a0b58919 ("drivers: gpio: use devm_kzalloc")
introduce devm_kzalloc() for allocating the memory. In this case kfree
is not required to use. Above commit id introduced the bug that kfree
is not removed from the remove function.

This patch fix the above bug.

Signed-off-by: Varka Bhadram <varkab@cdac.in>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>