ARM: EXYNOS: use 'exynos4-sdhci' as device name for sdhci controllers

With the addition of platform specific driver data in the sdhci driver
for EXYNOS4 and EXYNOS5, the device name of sdhci controllers on EXYNOS4
and EXYNOS5 are changed accordingly.

Signed-off-by: Thomas Abraham <thomas.abraham@linaro.org>
[kgene.kim@samsung.com: re-worked on top of v3.4-rc2]
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>