ARM: S3C2443/S3C2416: add s3c_rtc_setname and rename rtc devices

As the S3C24xx SoCs use the same rtc device a renaming capability like in
the adc driver is necessary.

This patch adds a s3c_rtc_setname function and names the rtc devices for
S3C2443 and S3C2416 accordingly.

Signed-off-by: Heiko Stuebner <heiko@sntech.de>
Signed-off-by: Kukjin Kim <kgene.kim@samsung.com>