ARM: SAMSUNG: Add support s3c2416-adc for S3C2416/S3C2450

The ADC of the S3C2416/2450 SoC is 10 or 12 bit wide, has its
source selection in the register base+0x18 and its width
selection in bit 03 of the ADCCON register.

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