mmc: sdhci-s3c: Fix mmc card I/O problem

This patch fixes the problem in sdhci-s3c host driver for Samsung Soc's.
During the card identification stage the mmc core driver enumerates for
the best bus width in combination with the highest available data rate.
It starts enumerating from the highest bus width (8) to lowest width (1).

In case of few MMC cards the 4-bit bus enumeration fails and tries
the 1-bit bus enumeration. When switched to 1-bit bus mode the host driver
has to clear the previous bus width setting and apply the new setting.

The current patch will clear the previous bus mode and apply the new
mode setting.

Signed-off-by: Girish K S <girish.shivananjappa@linaro.org>
Acked-by: Jaehoon Chung <jh80.chung@samsung.com>
Cc: <stable@kernel.org>
Signed-off-by: Chris Ball <cjb@laptop.org>