mmc: s3cmci: Convert s3cmci driver to gpiolib API

The s3c2410_gpio* calls are obsolete and have been scheduled for
removal since several kernel releases. Remove them and use common
gpiolib API.

This patch is a prerequisite for removal of the S3C24XX SoC specific
arch/arm/plat-samsung/include/gpio-fns.h header.

Tested on Micro2440-SDK.

Signed-off-by: Sylwester Nawrocki <sylvester.nawrocki@gmail.com>
Signed-off-by: Chris Ball <cjb@laptop.org>