mmc: s5p_sdhci: support the Driver model for Exynos

mmc: s5p_sdhci: support the Driver model for Exynos

This patch support the driver model for s5p_sdhci controller.
To support the legacy model, maintained the existing code.

Note: If use the Driver Model, it needs to modify the device-tree.
In future, will update the Device-tree and enable the configuratioin.
(CONFIG_BLK, CONFIG_DM_MMC and CONFING_DM_MMC_OPS)

Signed-off-by: Jaehoon Chung <jh80.chung@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>
Acked-by: Minkyu Kang <mk7.kang@samsung.com>
Reviewed-by: Simon Glass <sjg@chromium.org>