mmc: sdhci-s3c: Use generic clock names for sdhci bus clock options

This patch modifies the driver to stop depending on the clock names
being passed from the platform and switch over to bus clock lookup
using generic clock names.

Signed-off-by: Rajeshwari Shinde <rajeshwari.s@samsung.com>
Acked-by: Chris Ball <cjb@laptop.org>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>