gpio: eic-sprd: remove unneeded platform_set_drvdata() call

The platform_set_drvdata() call was never used, ever since the driver was
originally added.
It looks like this copy+paste left-over. Possibly the author copied from a
driver that had this line, but also had a remove hook.

Reviewed-by: Alexandru Ardelean <alex@shruggie.ro>
Signed-off-by: Andrei Coardos <aboutphysycs@gmail.com>
Reviewed-by: Andy Shevchenko <andy@kernel.org>
Reviewed-by: Baolin Wang <baolin.wang@linux.alibaba.com>
Signed-off-by: Bartosz Golaszewski <bartosz.golaszewski@linaro.org>