i2c: designware: Use devm_platform_ioremap_resource() to simplify code

Use devm_platform_ioremap_resource() instead of
platform_get_resource() + devm_ioremap_resource().

Signed-off-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Signed-off-by: Wolfram Sang <wsa@kernel.org>