S5PC2XX: Rename S5pc2XX to exynos

As per new naming convention for Samsung SoC's, all Cortex-A9 and Cortex-A15
based SoC's will be classified under the name Exynos. Cortex-A9 and Cortex-A15
based SoC's will be sub-classified as Exynos4 and Exynos5 respectively.

In order to better adapt and reuse code across various upcoming Samsung Exynos
based boards, all uses of s5pc210 prefix/suffix/directory-names are renamed in
this patch. s5pc210 is renamed as exynos4210 and S5PC210/s5pc210 suffix/prefix
are renamed as exynos4/EXYNOS4.

Signed-off-by: Chander Kashyap <chander.kashyap@linaro.org>
Signed-off-by: Minkyu Kang <mk7.kang@samsung.com>