i2c: s3c2410: Convert to use GPIO descriptors

The S3C2410 does some funny dance around its pins:
- First try to call back to the platform to get and control
  some GPIO pins
- If this doesn't work, it tries to get a pin control handle
- If this doesn't work, it retrieves two GPIOs from the device
  tree node and does nothing with them

If we're gonna retrieve two GPIOs and do nothing with them, we
might as well do it using the GPIO descriptor API. When we use
the resource management API, the code gets smaller.

Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Acked-by: Krzysztof Kozlowski <krzk@kernel.org>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>